MDMA pharmacology


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On Site Link: MDMA (Ecstasy) Metabolites and Neurotoxicity

On Site Link: MDMA and Neurotoxicity

Kantor, L., Gnegy, M. E.
Protein Kinase C Inhibitors Block Amphetamine-Mediated Dopamine Release in Rat Striatal Slices
J Pharmacol Exp Ther 1998 284: 592-598
"The stimulant drug amphetamine is postulated to enhance dopamine release through the plasmalemmal dopamine transporter by an exchange diffusion with synaptosomal dopamine. Because protein kinase C has been shown to have an effect on dopamine transporter activity, we examined the effect of protein kinase C inhibitors on endogenous dopamine release stimulated by amphetamine in perfused rat striatal slices. At concentrations of 1 microM, the selective protein kinase C inhibitors chelerythrine, Ro31-8220 and calphostin C nearly completely inhibited endogenous dopamine release elicited by 1 microM amphetamine. The inactive analog bisindoylmaleimide V had no effect. Extracellular Ca++ was not required for the effect of the inhibitors. The importance of vesicular dopamine release was examined by determining inhibitor activity in reserpine-treated rats. Dopamine release elicited by 1 microM amphetamine was not significantly altered in reserpine-treated rats compared with control animals. Ro31-8220 at 1 microM completely blocked amphetamine-induced dopamine release in reserpine-treated rats. Activation of protein kinase C with 250 nM of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate increased dopamine release, and the release was not additive with 1 microM amphetamine. Both chelerythrine and Ro31-8220 at 1 microM increased [3H]dopamine uptake by 17% and 30%, respectively, whereas a brief exposure to 12-O-tetradecanoylphorbol 13-acetate slightly inhibited [3H]dopamine uptake. Our results suggest that amphetamine-mediated dopamine release through the plasmalemmal transporter is highly dependent on protein kinase C activity." [Full Text]

Kramer HK, Poblete JC, Azmitia EC.
3,4-Methylenedioxymethamphetamine ('Ecstasy') promotes the translocation of protein kinase C (PKC): requirement of viable serotonin nerve terminals.
Brain Res 1995 May 22;680(1-2):1-8
"The metabolic effects of the neurotoxic, ring-substituted amphetamine 3,4-methylenedioxy-methamphetamine (MDMA or 'Ecstasy') were examined in vivo. In this study, we focused on the ability of MDMA to induce a translocation of the calcium and phospholipid-dependent protein kinase C (PKC) from the cytosol to the cortical plasma membrane. Two injections of MDMA (20 mg/kg; 10 h apart; s.c.) increased the density of membrane bound PKC sites by 48.0% over saline treated animals without mediating a significant change in ligand ([3H]phorbol 12,13 dibutyrate; [3H]PDBu) affinity. Longer drug treatments (8 x 20 mg/kg) induced a lasting (up to 5 days post-treatment) increase in the density of membrane-bound PKC. Prior destruction of cortical 5-HT nerve terminals with p-chloroamphetamine (PCA) prevents this effect and suggests that viable 5-HT uptake sites are essential for MDMA-induced PKC translocation. These results demonstrate that MDMA-induced PKC translocation is mediated by viable cortical 5-HT nerve terminals, and that prolonged kinase activation may contribute to MDMA-induced serotonergic neurotoxicity." [Abstract] [PDF]

Kramer HK, Poblete JC, Azmitia EC.
Characterization of the translocation of protein kinase C (PKC) by 3,4-methylenedioxymethamphetamine (MDMA/ecstasy) in synaptosomes: evidence for a presynaptic localization involving the serotonin transporter (SERT).
Neuropsychopharmacology 1998 Oct;19(4):265-77
"3, 4-methylenedioxymethamphetamine (MDMA or Ecstasy) is a substituted amphetamine whose acute and long-term effects on the serotonin system are dependent on an interaction with the 5-HT uptake transporter (SERT). Although much of the work dedicated to the study of this compound has focused on its ability to release monoamines, this drug has many important metabolic consequences on neurons and glial cells. The identification of these physiological responses will help to bridge the gap that exists in the information between the acute and neurotoxic effects of amphetamines. Substituted amphetamines have the ability to produce a long-term translocation of protein kinase C (PKC) in vivo, and this action may be crucial to the development of serotonergic neurotoxicity. Our earlier results suggested that PKC activation occurred through pre- and postsynaptic mechanisms. Because the primary site of action of these drugs is the 5-HT transporter, we now expand on our previous results and attempt to characterize MDMA's ability to translocate PKC within cortical 5-HT nerve terminals. In synaptosomes, MDMA produced a concentration-dependent increase in membrane-bound PKC (as measured by 3H-phorbol 12, 13 dibutyrate, 3H-PDBu) bindings sites. This response was abolished by cotreatment with the specific serotonin reuptake inhibitor (SSRI), fluoxetine, but not by the 5-HT2A/2C antagonist, ketanserin. In contrast, full agonists to 5-HT1A and 5-HT2 receptors did not produce significant PKC translocation. MDMA-mediated PKC translocation also requires the presence of extracellular calcium ions. Using assay conditions where extracellular calcium was absent prevented in vitro activation of PKC by MDMA. Prolonged PKC translocation has been hypothesized to contribute to the calcium-dependent neurotoxicity produced by substituted amphetamines. In addition, many physiological processes within 5-HT nerve terminals, including 5-HT reuptake and vesicular serotonin release, are susceptible to modification by PKC-dependent protein phosphorylation. Our results suggest that prolonged activation of PKC within the 5-HT nerve terminal may contribute to lasting changes in the homeostatic function of 5-HT neurons, leading to the degeneration of specific cellular elements after repeated MDMA exposure." [Abstract] [PDF]

Hansen, J. Paul, Riddle, Evan L., Sandoval, Veronica, Brown, Jeffrey M., Gibb, James W., Hanson, Glen R., Fleckenstein, Annette E.
Methylenedioxymethamphetamine Decreases Plasmalemmal and Vesicular Dopamine Transport: Mechanisms and Implications for Neurotoxicity
J Pharmacol Exp Ther 2002 300: 1093-1100
"Administration of a high-dose regimen of methamphetamine (METH) rapidly and profoundly decreases plasmalemmal and vesicular dopamine (DA) transport in the striatum, as assessed in synaptosomes and purified vesicles, respectively. To determine whether these responses were common to other amphetamines of abuse, effects of methylenedioxymethamphetamine (MDMA) on the plasmalemmal DA transporter (DAT) and vesicular monoamine transporter-2 (VMAT-2) were assessed. Similar to effects of METH reported previously, multiple high-dose MDMA administrations rapidly (within 1 h) decreased plasmalemmal DA uptake, as assessed ex vivo in synaptosomes prepared from treated rats. Unlike effects of multiple METH injections, this deficit was reversed completely 24 h after drug treatment. Also in contrast to effects of multiple METH injections, 1) MDMA caused little or no decrease in binding of the DAT ligand WIN35428, and 2) neither prevention of hyperthermia nor prior depletion of DA prevented the MDMA-induced reduction in plasmalemmal DA transport. However, a role for phosphorylation was suggested because pretreatment with protein kinase C inhibitors attenuated the deficit caused by MDMA in an in vitro model system. In addition to affecting DAT function, MDMA rapidly decreased vesicular DA transport as assessed in striatal vesicles prepared from treated rats. Unlike effects of multiple METH injections reported previously, this decrease partially recovered by 24 h after drug treatment. Taken together, these results reveal several differences between effects of MDMA and previously reported METH on DAT and VMAT-2; differences that may underlie the dissimilar neurotoxic profile of these agents." [Full Text]

Giambalvo CT.
Mechanisms underlying the effects of amphetamine on particulate PKC activity.
Synapse. 2004 Feb;51(2):128-39.
Amphetamine stimulates particulate protein kinase C (PKC) activity that is associated with the outward-transport of dopamine (DA) (Giambalvo [2003] Synapse 49:125-133). This stimulatory effect requires intracellular calcium ([Ca](i)) and endogenous DA and when DA release is diminished, the inward-transport of amphetamine inhibits PKC activity. This study examines the mechanisms involved. It was found that synaptoneurosomes incubated with amphetamine showed a dose-dependent increase in phospholipase C and A(2) activities. Furthermore, pretreatments with the phospholipase C inhibitor D609 or the phospholipase A(2) inhibitors quinacrine or p-bromophenacylbromide attenuated the amphetamine-induced increase in PKC activity. This suggests that both phospholipases were essential for the amphetamine-induced increase in PKC activity. The Na/Ca antiporter was also involved, since pretreatment with amiloride or benzamil attenuated the amphetamine-induced increase in PKC activity. Since these drugs by themselves increased PKC activity, the return to basal activity after addition of amphetamine suggests that, in the absence of Na/Ca exchange, amphetamine had an inhibitory effect on PKC activity. This inhibitory effect might be due to the activation of phospholipase A(2) through an increase in intracellular pH induced by amphetamine. This was supported by the finding that pretreatment with dimethylamiloride, an inhibitor of the Na/H antiporter that increases intracellular [H(+)], attenuated the effects of amphetamine on PKC activity. Other drugs that decrease intracellular [H(+)] (ammonia, monensin) also inhibited PKC activity without Ca. In contrast to amphetamine, monensin had no effect on PKC activity with Ca. This could be related to its large differential effects on phospholipase A(2) vs. phospholipase C activity. Thus, the monensin-mediated decrease in PKC activity seen without Ca was partially attenuated by pretreatment with quinacrine. Furthermore, when Na/Ca antiporter was inhibited with benzamil, monensin inhibited PKC activity. These results suggest that amphetamine, as well as monensin, may have dual effects on PKC activity, a Ca-dependent stimulatory effect via phospholipase C, and an inhibitory effect via phospholipase A(2). [Abstract]

Schuldiner, S, Steiner-Mordoch, S, Yelin, R, Wall, SC, Rudnick, G
Amphetamine derivatives interact with both plasma membrane and secretory vesicle biogenic amine transporters
Mol Pharmacol 1993 44: 1227-1231
"The interaction of fenfluramine, 3,4-methylenedioxymethamphetamine (MDMA), and p-chloroamphetamine (PCA) with the platelet plasma membrane serotonin transporter and the vesicular amine transporter were studied using both transport and binding measurements. Fenfluramine is apparently a substrate for the plasma membrane transporter, and consequently inhibits both serotonin transport and imipramine binding. Moreover, fenfluramine exchanges with internal [3H]serotonin in a plasma membrane transporter-mediated reaction that requires NaCl and is blocked by imipramine. These properties are similar to those of MDMA and PCA as previously described. In adrenal chromaffin granule membrane vesicles containing the vesicular amine transporter, fenfluramine inhibited serotonin transport and dissipated the transmembrane pH difference (delta pH) that drives amine uptake. The use of [3H]reserpine-binding measurements to determine drug interaction with the vesicular amine transporter allowed assessment of the relative ability of MDMA, PCA, and fenfluramine to bind to the substrate site of the vesicular transporter. These measurements permit a distinction between inhibition of vesicular serotonin transport by directly blocking vesicular amine transport and by dissipating delta pH. The results indicate that MDMA and fenfluramine inhibit by both mechanisms but PCA dissipates delta pH without blocking vesicular amine transport directly." [Abstract]

Sammanda Ramamoorthy, Elena Giovanetti, Yan Qian, and Randy D. Blakely
Phosphorylation and Regulation of Antidepressant-sensitive Serotonin Transporters
J. Biol. Chem. 273: 2458-2466, 1998.
"Antidepressant-sensitive serotonin (5-hydroxytryptamine, 5HT) transporters (SERTs) are responsible for efficient synaptic clearance of extracellular 5HT. Previously (Qian, Y., Galli, A., Ramamoorthy, S., Risso, S., DeFelice, L. J., and Blakely, R. D. (1997) J. Neurosci. 17, 45-47), we demonstrated that protein kinase (PKC)-linked pathways in transfected HEK-293 cells lead to the internalization of cell-surface human (h) SERT protein and a reduction in 5HT uptake capacity. In the present study, we report that PKC activators rapidly, and in a concentration-dependent manner, elevate the basal level of hSERT phosphorylation 5-6-fold. Similarly, protein phosphatase (PP1/PP2A) inhibitors down-regulate 5HT transport and significantly elevate hSERT 32P incorporation, effects that are additive with those of PKC activators. Moreover, hSERT phosphorylation induced by beta-phorbol 12-myristate 13-acetate is abolished selectively by the PKC inhibitors staurosporine and bisindolylmaleimide I, whereas hSERT phosphorylation induced by phosphatase inhibitors is insensitive to these agents at comparable concentrations. Protein kinase A and protein kinase G activators fail to acutely down-regulate 5HT uptake but significantly enhance hSERT phosphorylation. Basal hSERT and okadaic acid-induced phosphorylation were insensitive to chelation of intracellular calcium and Ca2+/calmodulin-dependent protein kinase inhibitors. Together these results reveal hSERT to be a phosphoprotein whose phosphorylation state is likely to be tightly controlled by multiple kinase and phosphatase pathways that may also influence the transporter's regulated trafficking." [Full Text]

Feuerstein TJ, Allgaier C, Hertting G.
Possible involvement of protein kinase C (PKC) in the regulation of electrically evoked serotonin (5-HT) release from rabbit hippocampal slices.
Eur J Pharmacol 1987 Jul 23;139(3):267-72
"Protein kinase C (PKC)-activating phorbol esters enhanced the electrically evoked 5-HT release from rabbit hippocampal slices preincubated with [3H]5-HT. The release was diminished by polymyxin B, an inhibitor of PKC. These results are compatible with a stimulatory effect of PKC on the 5-HT release induced by action potentials. The mutual effects of PKC affecting drugs on 5-HT release suggest a functional but not a competitive interaction. The attenuation or the enhancement of effects of 5-HT autoreceptor ligands at various 5-HT biophase concentrations found after PKC-affecting drugs are in line with the view that autoreceptor-mediated events are not directly influenced by the enzyme PKC." [Abstract]

Sitte, Harald H., Hiptmair, Birgit, Zwach, Julia, Pifl, Christian, Singer, Ernst A., Scholze, Petra
Quantitative Analysis of Inward and Outward Transport Rates in Cells Stably Expressing the Cloned Human Serotonin Transporter: Inconsistencies with the Hypothesis of Facilitated Exchange Diffusion
Mol Pharmacol 2001 59: 1129-1137
"Quantitative aspects of inward and outward transport of substrates by the human plasmalemmal serotonin transporter (hSERT) were investigated. Uptake and superfusion experiments were performed on human embryonic kidney 293 cells permanently expressing the hSERT using [(3)H]serotonin (5-HT) and [(3)H]1-methyl-4-phenylpyridinium (MPP(+)) as substrates. Saturation analyses rendered K(m) values of 0.60 and 17.0 microM for the uptake of [(3)H]5-HT and [(3)H]MPP(+), respectively. Kinetic analysis of outward transport was performed by prelabeling the cells with increasing concentrations of the two substrates and exposing them to a saturating concentration of p-chloroamphetamine (PCA; 10 microM). Apparent K(m) values for PCA induced transport were 564 microM and about 7 mM intracellular [(3)H]5-HT and [(3)H]MPP(+), respectively. Lowering the extracellular Na(+) concentrations in uptake and superfusion experiments revealed differential effects on substrate transport: at 10 mM Na(+) the K(m) value for [(3)H]5-HT uptake increased approximately 5-fold and the k value remained unchanged. The K(m) value for [(3)H]MPP(+) uptake also increased, but the V(max) value was reduced by 50%. When efflux was studied at saturating prelabeling conditions of both substrates, PCA as well as unlabeled 5-HT and MPP(+) (all substances at saturating concentrations) induced the same efflux at 10 mM and 120 mM Na(+). Thus, notwithstanding a 50% reduction in the V(max) value of transport into the cell, MPP(+) was still able to induce maximal outward transport of either substrate. Thus, hSERT-mediated inward and outward transport seems to be independently modulated and may indicate inconsistencies with the classical model of facilitated exchange diffusion." [Full Text]

Petra Scholze, Lene Nørregaard, Ernst A. Singer, Michael Freissmuth, Ulrik Gether, and Harald H. Sitte
The Role of Zinc Ions in Reverse Transport Mediated by Monoamine Transporters
J. Biol. Chem. 277: 21505-21513, 2002.
"The human dopamine transporter (hDAT) contains an endogenous high affinity Zn2+ binding site with three coordinating residues on its extracellular face (His193, His375, and Glu396). Upon binding to this site, Zn2+ causes inhibition of [3H]1-methyl-4-phenylpyridinium ([3H]MPP+) uptake. We investigated the effect of Zn2+ on outward transport by superfusing hDAT-expressing HEK-293 cells preloaded with [3H]MPP+. Although Zn2+ inhibited uptake, Zn2+ facilitated [3H]MPP+ release induced by amphetamine, MPP+, or K+-induced depolarization specifically at hDAT but not at the human serotonin and the norepinephrine transporter (hNET). Mutation of the Zn2+ coordinating residue His(193) to Lys (the corresponding residue in hNET) eliminated the effect of Zn2+ on efflux. Conversely, the reciprocal mutation (K189H) conferred Zn2+ sensitivity to hNET. The intracellular [3H]MPP+ concentration was varied to generate saturation isotherms; these showed that Zn2+ increased V(max) for efflux (rather than K(M-Efflux-intracellular)). Thus, blockage of inward transport by Zn2+ is not due to a simple inhibition of the transporter turnover rate. The observations provide evidence against the model of facilitated exchange-diffusion and support the concept that inward and outward transport represent discrete operational modes of the transporter. In addition, they indicate a physiological role of Zn2+, because Zn2+ also facilitated transport reversal of DAT in rat striatal slices." [Full Text]

Khoshbouei H, Wang H, Lechleiter JD, Javitch JA, Galli A.
Amphetamine-induced DA efflux: A voltage sensitive and intracellular Na+-dependent mechanism.
J Biol Chem 2003 Jan 29; [epub ahead of print]
"Amphetamine (AMPH) elicits its behavioral effects by acting on the dopamine (DA) transporter (DAT) to induce DA overflow into the synaptic cleft. Facilitated exchange diffusion is the classical model used to describe AMPH-induced DA efflux. This model hypothesizes that AMPH-induced DA efflux is mediated by DAT and results from transport of AMPH into the cell followed by a counter movement of DA out to the extracellular compartment. To further characterize the action of AMPH, we used the patch clamp technique in the whole-cell configuration combined with amperometry on HEK-293 cells stably transfected with the human DAT (DAT cells). In DAT cells, AMPH-induced DAT-mediated currents were blocked by cocaine. We demonstrate that DA efflux mediated by DAT is voltage dependent, electrogenic, and dependent on intracellular Na+ concentration in the recording electrode. Intracellular Na+ fluorescence, as measured by confocal microscopy using a Na+ sensitive dye, was enhanced by AMPH application. Furthermore, the ability of AMPH to induce DA efflux was regulated by intracellular Na+ concentration and correlated with the size of the DAT-mediated AMPH-induced ion flux across the plasma membrane. In the absence of intracellular Na+, but in the presence of high intracellular Cl-, AMPH-induced inward currents elicited DA efflux proportionally to their dimension and duration. Thus, we propose that AMPH-induced DA efflux depends on two-correlated transporter processes. First, AMPH binds to the DAT and is transported, thereby causing an inward current. Second, because of this AMPH-induced inward current, Na+ becomes more available intracellularly to the DAT, thereby enhancing DAT-mediated reverse transport of DA." [Abstract/ Full Text]

Connor CE, Kuczenski R.
Evidence that amphetamine and Na+ gradient reversal increase striatal synaptosomal dopamine synthesis through carrier-mediated efflux of dopamine.
Biochem Pharmacol 1986 Sep 15;35(18):3123-30
"Amphetamine (AMPH) releases dopamine (DA) from striatal synaptosomes and concomitantly increases DA synthesis. Since AMPH may release DA through carrier-mediated diffusion via reversal of the DA uptake system, the increase in DA synthesis might depend on a functioning uptake carrier. Consistent with such a mechanism, the uptake inhibitors nomifensine (NMF) and benztropine (BZT) completely prevented the AMPH-induced increase in DA synthesis at concentrations known to inhibit DA uptake. Changes in the Na+ gradient across the synaptosomal membrane also promote DA release, since DA and Na+ are cotransported by the neuronal uptake carrier. Incubation of synaptosomes in medium containing decreasing Na+ increased DA synthesis inversely proportional to Na+ over the range 128 to 20 mM. Similarly, incubations in the presence of 10(-4) M ouabain to inhibit Na+, K+-ATPase and allow intracellular accumulation of Na+ also increased DA synthesis. These changes in DA synthesis could also be prevented by BZT and were non-additive with the AMPH-induced increase in DA synthesis. However, a concentration of ouabain (10(-6) M) which by itself did not increase DA synthesis, and does not promote DA release, potentiated the AMPH-induced increase in DA synthesis. Further, the increased DA synthesis promoted by all three manipulations was only marginally dependent on the presence of Ca2+ in the incubation medium. However, at 5 and 10 mM Na+, a second component of increased DA synthesis was observed which was insensitive to BZT, but was prevented by Ca2+ removal. These results suggest that the increase in DA synthesis, and presumably DA release promoted by AMPH, lowered Na+, and ouabain, depend on the availability of the DA carrier at the internal face of the neuronal membrane and the intracellular content of Na+. The second component of increased DA synthesis which is evident at 5 and 10 mM Na+ is discussed in terms of a possible Ca2+-mediated change in DA synthesis which is independent of the DA carrier." [Abstract]

Kantor, Lana, Hewlett, G. H. Keikilani, Park, Yang Hae, Richardson-Burns, Sarah M., Mellon, Mathew J., Gnegy, Margaret E.
Protein Kinase C and Intracellular Calcium Are Required for Amphetamine-Mediated Dopamine Release via the Norepinephrine Transporter in Undifferentiated PC12 Cells
J Pharmacol Exp Ther 2001 297: 1016-1024
"The role of protein kinase C and intracellular Ca(2+) on amphetamine-mediated dopamine release through the norepinephrine plasmalemmal transporter in undifferentiated PC12 cells was investigated. The selective protein kinase C inhibitor chelerythrine completely inhibited endogenous dopamine release elicited by 1 microM amphetamine. Direct activation of protein kinase C increased dopamine release in a Ca(2+)-insensitive, imipramine-sensitive manner and the release was not additive with amphetamine. Exocytosis was not involved since these events were not altered by either deletion of extracellular Ca(2+) or reserpine pretreatment. Down-regulation of protein kinase C activity by long-term phorbol ester treatment resulted in a dramatic decrease in amphetamine-mediated dopamine release with no apparent effect on [(3)H]dopamine uptake. To more completely examine a role for Ca(2+), intracellular Ca(2+) was chelated in the cells. Depletion of intracellular Ca(2+) considerably decreased dopamine release in response to 1 microM amphetamine compared with vehicle-treated cells, but had no effect on the [(3)H]dopamine uptake. Thus, our results suggest that amphetamine-mediated dopamine release through the plasmalemmal norepinephrine transporter is highly dependent on protein kinase C activity and intracellular but not extracellular Ca(2+). Furthermore, protein kinase C and intracellular Ca(2+) appear to regulate [(3)H]dopamine inward transport and amphetamine-mediated outward transport of dopamine independently in PC12 cells." [Full Text]

Koch S, Galloway MP.
MDMA induced dopamine release in vivo: role of endogenous serotonin.
J Neural Transm 1997;104(2-3):135-46
"Acting as a substrate at the serotonin (5-HT) transporter, (+)-MDMA (3,4-methylenedioxymethamphetamine), is a potent releaser of 5-HT and causes toxicity to 5-HT neurons after repeated exposure. (+)-MDMA also releases dopamine (DA), although with less potency. Since we have shown previously that the intrastriatal application of 5-HT facilities DA release, it was hypothesized that increased release of striatal 5-HT after MDMA may influence extracellular levels of DA. Using microdialysis in vivo, we found that (+)-MDMA (4.7 mumol/kg, i.v.) administration increased extracellular striatal DA levels to 501% of control (p < 0.01, n = 12). However, in the presence of fluoxetine (14.4 mumol/kg, s.c.), which prevents (+)-MDMA effects on 5-HT release, the (+)-MDMA-induced increase in DA was significantly less (to 375% of control, p < 0.05, vs. no fluoxetine, n = 8). In vitro studies with striatal slices, to test drug selectivity, showed that (+)-MDMA (0.3-3 microM) increased extracellular levels of both DA and 5-HT in a dose-dependent manner. Fluoxetine (3 microM) completely blocked the effects of (+)-MDMA on 5-HT release, but did not alter (+)-MDMA-induced DA release in vitro. The selective DA transport inhibitor GBR-12909 (1 microM), blocked (+)-MDMA's effect on DA release. It is concluded that 5-HT release after (+)-MDMA treatment partially contributes to (+)-MDMA's effect on DA release in vivo." [Abstract]

Nash JF, Brodkin J.
Microdialysis studies on 3,4-methylenedioxymethamphetamine-induced dopamine release: effect of dopamine uptake inhibitors.
J Pharmacol Exp Ther 1991 Nov;259(2):820-5
"The effect of dopamine (DA) and serotonin (5-HT) uptake inhibitors on 3,4-methylenedioxymethamphetamine (MDMA)-induced increase in DA efflux was studied using in vivo microdialysis. MDMA was infused directly into the anterolateral striatum via the dialysis probe. The local administration of MDMA produced a dose- and time-dependent increase in the extracellular concentration of DA in the striatum. Peripheral administration of the DA uptake blockers, mazindol (5 mg/kg, i.p.) or GBR 12909 (10 mg/kg, i.p.), produced a slight but significant increase in the extracellular concentration of DA. Moreover, pretreatment with either mazindol or GBR 12909 30 min before the infusion of MDMA (10 microM) significantly attenuated the MDMA-induced increase in the extracellular concentration of DA. Pretreatment with fluoxetine (10 mg/kg, i.p.), a 5-HT uptake blocker, 30 min before the infusion of MDMA produced a slight but significant inhibition of MDMA-induced increase in DA concentration. In contrast, pretreatment with the 5-HT2/1C antagonist, ketanserin (3 mg/kg, i.p.), had no significant effect on the increase in DA concentration produced by the local administration of MDMA. These data are suggestive that MDMA increases the concentration of DA in the striatum, in part, via a carrier-mediated mechanism which is largely independent of its effects on 5-HT release." [Abstract]

Camarero J, Sanchez V, O'Shea E, Green AR, Colado MI.
Studies, using in vivo microdialysis, on the effect of the dopamine uptake inhibitor GBR 12909 on 3,4-methylenedioxymethamphetamine ('ecstasy')-induced dopamine release and free radical formation in the mouse striatum.
J Neurochem 2002 Jun;81(5):961-72
"The present study examined the mechanisms by which 3,4-methylenedioxymethamphetamine (MDMA) produces long-term neurotoxicity of striatal dopamine neurones in mice and the protective action of the dopamine uptake inhibitor GBR 12909. MDMA (30 mg/kg, i.p.), given three times at 3-h intervals, produced a rapid increase in striatal dopamine release measured by in vivo microdialysis (maximum increase to 380 +/- 64% of baseline). This increase was enhanced to 576 +/- 109% of baseline by GBR 12909 (10 mg/kg, i.p.) administered 30 min before each dose of MDMA, supporting the contention that MDMA enters the terminal by diffusion and not via the dopamine uptake site. This, in addition to the fact that perfusion of the probe with a low Ca(2+) medium inhibited the MDMA-induced increase in extracellular dopamine, indicates that the neurotransmitter may be released by a Ca(2+) -dependent mechanism not related to the dopamine transporter. MDMA (30 mg/kg x 3) increased the formation of 2,3-dihydroxybenzoic acid (2,3-DHBA) from salicylic acid perfused through a probe implanted in the striatum, indicating that MDMA increased free radical formation. GBR 12909 pre-treatment attenuated the MDMA-induced increase in 2,3-DHBA formation by approximately 50%, but had no significant intrinsic radical trapping activity. MDMA administration increased lipid peroxidation in striatal synaptosomes, an effect reduced by approximately 60% by GBR 12909 pre-treatment. GBR 12909 did not modify the MDMA-induced changes in body temperature. These data suggest that MDMA-induced toxicity of dopamine neurones in mice results from free radical formation which in turn induces an oxidative stress process. The data also indicate that the free radical formation is probably not associated with the MDMA-induced dopamine release and that MDMA does not induce dopamine release via an action at the dopamine transporter." [Abstract]

Metzger RR, Hanson GR, Gibb JW, Fleckenstein AE.
3-4-Methylenedioxymethamphetamine-induced acute changes in dopamine transporter function.
Eur J Pharmacol 1998 May 22;349(2-3):205-10
"The acute effects of the amphetamine designer drug, 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy'), on dopamine transporter function in rat striatum were investigated and compared to other psychostimulants known to influence monoaminergic systems. A single MDMA injection (10-20 mg/kg; s.c.) caused a dose-related decrease in [3H]dopamine uptake into striatal synaptosomes prepared 1 h after MDMA administration. This rapid effect on [3H]dopamine uptake returned to control levels 24 h after treatment. A single administration of other amphetamine analogs, such as methamphetamine (15 mg/kg; s.c.), p-chloroamphetamine (10 mg/kg; i.p.) or methcathinone (30 mg/kg; s.c.), also rapidly decreased striatal [3H]dopamine uptake. In contrast, a single or multiple administrations of cocaine (30 mg/kg; i.p.) had no effect on [3H]dopamine transport into striatal synaptosomes. These changes in dopamine transporter activity by the amphetamine analogs may occur via reactive oxygen species-mediated mechanisms." [Abstract]

Shankaran M, Gudelsky GA.
Effect of 3,4-methylenedioxymethamphetamine (MDMA) on hippocampal dopamine and serotonin.
Pharmacol Biochem Behav 1998 Dec;61(4):361-6
"The 3,4-methylenedioxymethamphetamine (MDMA)-induced increase in the extracellular concentration of dopamine and the long-term depletion of 5-HT were studied in the hippocampus of the rat brain. MDMA produced a dose-dependent increase in the extracellular concentration of dopamine in the hippocampus, as well as in the striatum. The MDMA-induced increase in the extracellular concentration of dopamine in the hippocampus, but not in the striatum, was suppressed in rats treated with the norepinephrine uptake inhibitor, desipramine, and in rats in which noradrenergic neurons in the hippocampus were lesioned with DSP4 (N-(2- chloroethyl)-N-ethyl-2-bromo benzylamine). However, the long-term depletion of 5-HT in the hippocampus produced by MDMA was unaltered in desipramine-treated rats. These results are supportive of the view that the MDMA-induced increase in the extracellular concentration of dopamine in the hippocampus is the result of an enhanced release of dopamine from noradrenergic neurons. In addition, the MDMA-induced depletion of 5-HT in the hippocampus appears not to involve dopamine-initiated processes, because suppression of MDMA-induced dopamine release did not attenuate the long-term depletion of 5-HT in the hippocampus." [Abstract]

Fitzgerald JL, Reid JJ.
Effects of methylenedioxymethamphetamine on the release of monoamines from rat brain slices.
Eur J Pharmacol 1990 Nov 27;191(2):217-20
"The effects of 3,4-methylenedioxymethamphetamine (MDMA) on monoamine release were investigated in superfused slices of rat striatum and hippocampus. MDMA (10 microM) increased the resting release of radioactivity from slices incubated in [3H]dopamine, [3H]5-hydroxytryptamine or [3H]noradrenaline. These effects of MDMA (10 microM) were blocked by the neuronal uptake inhibitors, cocaine (10 microM), fluoxetine (1 microM) and desmethylimipramine (1 microM), respectively. MDMA (10 microM) enhanced the stimulation-induced efflux of radioactivity from slices incubated in [3H]noradrenaline but not from slices incubated in [3H]5-hydroxytryptamine or [3H]dopamine. These results demonstrate for the first time a direct noradrenaline-releasing action of MDMA and differential effects of MDMA on the stimulation-induced release of noradrenaline, dopamine and 5-hydroxytryptamine from rat superfused brain slices." [Abstract]

Kanthasamy A, Sprague JE, Shotwell JR, Nichols DE.
Unilateral infusion of a dopamine transporter antisense into the substantia nigra protects against MDMA-induced serotonergic deficits in the ipsilateral striatum.
Neuroscience 2002;114(4):917-24
"The present study was designed to elucidate the consequences of antisense oligonucleotide-mediated knockdown of striatal dopamine reuptake transporters on 3,4-methylenedioxymethamphetamine (MDMA)-induced neurotoxicity. Antisense oligonucleotide complementary to the mRNA translational start site of the rat dopamine transporter was delivered by constant (7 days) intranigral infusion with an osmotic minipump. Delivery of the antisense oligonucleotide by this method resulted in a 70% reduction in the density of the dopamine transporter in the ipsilateral striatum, as measured by [(3)H]mazindol binding. The effect of this transporter knockdown on MDMA-induced serotonergic neurotoxicity was then examined. MDMA (2x20 mg/kg, s.c., given 12 h apart) administered to control rats produced hyperthermia following the first dose and led to a 45-50% reduction in striatal serotonin, 5-hydroxyindoleacetic acid, and serotonin reuptake transporter density 1 week after the second dose. Conversely, in antisense-, but not missense-treated rats, a significant attenuation of MDMA-induced neurotoxicity was observed only in the ipsilateral striatum. The hyperthermic response elicited by MDMA was not altered by prior administration of antisense. In vivo microdialysis revealed that the antisense treatment attenuated MDMA-induced dopamine release in the ipsilateral striatum.These results suggest that the dopamine transporter plays an essential role in the neurodegeneration induced by MDMA, and provides additional support for the hypothesis that extracellular dopamine is involved in the neurotoxic process, at least in the striatum." [Abstract]

Shankaran M, Yamamoto BK, Gudelsky GA.
Mazindol attenuates the 3,4-methylenedioxymethamphetamine-induced formation of hydroxyl radicals and long-term depletion of serotonin in the striatum.
J Neurochem 1999 Jun;72(6):2516-22
"The formation of hydroxyl radicals following the systemic administration of 3,4-methylenedioxymethamphetamine (MDMA) was studied in the striatum of the rat by quantifying the stable adducts of salicylic acid and D-phenylalanine, namely, 2,3-dihydroxybenzoic acid (2,3-DHBA) and p-tyrosine, respectively. The repeated administration of MDMA produced a sustained increase in the extracellular concentration of 2,3-DHBA and p-tyrosine, as well as dopamine. The MDMA-induced increase in the extracellular concentration of both dopamine and 2,3-DHBA was suppressed in rats treated with mazindol, a dopamine uptake inhibitor. Mazindol also attenuated the long-term depletion of serotonin (5-HT) in the striatum produced by MDMA without altering the acute hyperthermic response to MDMA. These results are supportive of the view that MDMA produces a dopamine-dependent increase in the formation of hydroxyl radicals in the striatum that may contribute to the mechanism whereby MDMA produces a long-term depletion of brain 5-HT content." [Abstract]

Al-Sahli W, Ahmad H, Kheradmand F, Connolly C, Docherty JR.
Effects of methylenedioxymethamphetamine on noradrenaline-evoked contractions of rat right ventricle and small mesenteric artery.
Eur J Pharmacol 2001 Jun 22;422(1-3):169-74
"We have compared the effects of methylenedioxymethamphetamine (MDMA) and cocaine on contractions to noradrenaline in 1 Hz paced rat right ventricular strips, and in rat small mesenteric artery and aorta. Noradrenaline increased the force of contraction of 1 Hz paced ventricular strips with a pD(2) (-log EC(50)) of 5.64+/-0.07. Both cocaine (10 microM) and MDMA (10 microM) significantly increased the potency of noradrenaline to 6.31+/-0.11 and 6.42+/-0.13, respectively. However, in the presence of cocaine (10 microM) which increased the potency of noradrenaline to 6.78+/-0.15, MDMA (10 microM) no longer increased the potency of noradrenaline (pD(2) of 6.78+/-0.32). Likewise, following chemical sympathectomy, MDMA failed to increase the potency of noradrenaline. The potency of the agonist isoprenaline, which is not a substrate for the noradrenaline transporter, was not increased by either cocaine or MDMA. In rat small mesenteric artery, but not aorta, MDMA and cocaine significantly increased the potency of noradrenaline, but in the presence of cocaine, MDMA had no further effect. Hence, MDMA shares with cocaine an ability to potentiate the actions of noradrenaline, an action in the case of MDMA which may involve competitive blockade of the noradrenaline transporter, rather than simply displacement of noradrenaline. Since cocaine is linked to an increased incidence of myocardial infarction, these results may have implications in terms of cardiac morbidity of MDMA." [Abstract]

Schuldiner S, Steiner-Mordoch S, Yelin R, Wall SC, Rudnick G.
Amphetamine derivatives interact with both plasma membrane and secretory vesicle biogenic amine transporters.
Mol Pharmacol 1993 Dec;44(6):1227-31
"The interaction of fenfluramine, 3,4-methylenedioxymethamphetamine (MDMA), and p-chloroamphetamine (PCA) with the platelet plasma membrane serotonin transporter and the vesicular amine transporter were studied using both transport and binding measurements. Fenfluramine is apparently a substrate for the plasma membrane transporter, and consequently inhibits both serotonin transport and imipramine binding. Moreover, fenfluramine exchanges with internal [3H]serotonin in a plasma membrane transporter-mediated reaction that requires NaCl and is blocked by imipramine. These properties are similar to those of MDMA and PCA as previously described. In adrenal chromaffin granule membrane vesicles containing the vesicular amine transporter, fenfluramine inhibited serotonin transport and dissipated the transmembrane pH difference (delta pH) that drives amine uptake. The use of [3H]reserpine-binding measurements to determine drug interaction with the vesicular amine transporter allowed assessment of the relative ability of MDMA, PCA, and fenfluramine to bind to the substrate site of the vesicular transporter. These measurements permit a distinction between inhibition of vesicular serotonin transport by directly blocking vesicular amine transport and by dissipating delta pH. The results indicate that MDMA and fenfluramine inhibit by both mechanisms but PCA dissipates delta pH without blocking vesicular amine transport directly." [Abstract]

Kantor L, Hewlett GH, Gnegy ME.
Enhanced amphetamine- and K+-mediated dopamine release in rat striatum after repeated amphetamine: differential requirements for Ca2+- and calmodulin-dependent phosphorylation and synaptic vesicles.
J Neurosci 1999 May 15;19(10):3801-8
"After cessation of repeated, intermittent amphetamine, we detected an emergent Ca2+-dependent component of amphetamine-induced dopamine release and an increase in calmodulin and Ca2+- and calmodulin-dependent protein kinase activity in rat striatum. This study examined the involvement of calmodulin-dependent protein kinase II (CaM kinase II) and synaptic vesicles in the enhanced Ca2+-dependent dopamine release in response to amphetamine or K+ in rat striatum. Rats were pretreated for 5 d with 2.5 mg/kg amphetamine or saline and withdrawn from drug for 10 d. The selective CaM kinase II inhibitor KN-93 (1 microM), but not the inactive analog KN-92, attenuated the Ca2+-dependent amphetamine-mediated dopamine release from amphetamine-pretreated rats but had no effect in saline-pretreated controls. [3H]Dopamine uptake was unaltered by repeated amphetamine or KN-93 and was Ca2+ independent. Striatal dopamine release stimulated by 50 mM KCl was enhanced twofold after repeated amphetamine compared with that in saline controls but was unaffected by KN-93. To examine the requirement for dopaminergic vesicles in the Ca2+-dependent dopamine release, we administered reserpine to saline- and amphetamine-pretreated rats 1 d before killing. Reserpine pretreatment did not affect amphetamine-mediated dopamine release from either pretreatment group but completely ablated K+-mediated dopamine release. Reserpine did not disrupt the ability of 1 microM KN-93 to block the Ca2+-dependent amphetamine-mediated dopamine release from amphetamine-pretreated rats. The results indicate that the enhanced dopamine release elicited by amphetamine from chronically treated rats is dependent on Ca2+- and calmodulin-dependent phosphorylation and is independent of vesicular dopamine storage. On the contrary, the enhanced depolarization-mediated vesicular dopamine release is independent of Ca2+- and calmodulin-dependent phosphorylation." [Abstract]

Copeland BJ, Vogelsberg V, Neff NH, Hadjiconstantinou M.
Protein kinase C activators decrease dopamine uptake into striatal synaptosomes.
J Pharmacol Exp Ther 1996 Jun;277(3):1527-32
"Incubation with either of the protein kinase C activators phorbol 12-myristate 13-acetate (PMA) and sn-1,2 dioctanoylglycerol (DiC8) decreased the uptake of dopamine into striatal synaptosomes, whereas the inactive phorbol ester 4 alpha-PMA had no effect. Washout of PMA and DiC8 failed to reverse the decrease in uptake. Kinetic analysis showed a decrease in the apparent V(max) for the transporter without changes in the K(m). Neither PMA nor DiC8 affected mazindol binding to the dopamine transporter. Preincubation with the protein kinase inhibitor staurosporine prevented the DiC8-induced decrease of dopamine uptake. Furthermore, the protein phosphatase inhibitor okadaic acid decreased dopamine uptake by itself and enhanced the DiC8-induced reduction of uptake. These findings support a role for protein kinase C in modulating dopamine transporter activity." [Abstract]

Cowell RM, Kantor L, Hewlett GH, Frey KA, Gnegy ME.
Dopamine transporter antagonists block phorbol ester-induced dopamine release and dopamine transporter phosphorylation in striatal synaptosomes.
Eur J Pharmacol 2000 Feb 11;389(1):59-65
"We have reported that inhibition of protein kinase C blocks the Ca(2+)-independent reverse transport of dopamine mediated by amphetamine. In this study we investigated whether activation of protein kinase C by 12-O-tetradecanoyl phorbol-13-acetate (TPA) would mediate dopamine release through the plasmalemmal dopamine transporter. TPA, at 250 nM, increased the release of dopamine from rat striatal slices and synaptosomes while the inactive phorbol ester, 4alpha-phorbol, was ineffective. The TPA-mediated dopamine release was independent of extracellular calcium and was blocked by a selective protein kinase C inhibitor, Ro31-8220. The dopamine transporter antagonists, cocaine and GBR 12935 blocked the TPA-mediated dopamine release. In addition, cocaine blocked TPA-mediated phosphorylation of the plasmalemmal dopamine transporter. These results suggest that activation of protein kinase C results in reverse transport of dopamine through the plasmalemmal dopamine transporter and the phosphorylated substrate could be the dopamine transporter." [Abstract]

Davis, ME, Patrick, RL
Diacylglycerol-induced stimulation of neurotransmitter release from rat brain striatal synaptosomes
J Neurochem 1990 54: 662-668
"These studies were undertaken to test the hypothesis that alterations in phosphatidylinositol metabolism can modulate neurotransmitter release in the central nervous system. The effects of 1,2- diacylglycerols (DAGs) on dopamine release in the rat central nervous system were determined by measuring dopamine release from rat striatal synaptosomes in response to two DAGs (sn-1,2-dioctanoylglycerol and 1- oleoyl-2-acetylglycerol) that can activate protein kinase C and one DAG (deoxydioctanoylglycerol) that does not activate this kinase. Dioctanoylglycerol and 1-oleoyl-2-acetylglycerol, at a concentration of 50 micrograms/ml, stimulated the release of labeled dopamine from striatal synaptosomes by 35-50 and 17%, respectively. Dioctanoylglycerol-induced release was also demonstrated for endogenous dopamine. In contrast, deoxydioctanoylglycerol (50 micrograms/ml) did not stimulate dopamine release. Dioctanoylglycerol-induced dopamine release was independent of external calcium concentration, indicating a utilization of internal calcium stores. Dioctanoylglycerol (50 micrograms/ml) also produced a 38% increase in labeled serotonin release from striatal synaptosomes. The addition of dioctanoylglycerol to the striatal supernatant fraction increased protein kinase C activity. These results are consistent with the concept that an increase in phosphatidylinositol metabolism can stimulate neurotransmitter release in the central nervous system via an increase in DAG concentration. The data suggest an involvement of protein kinase C in the DAG-induced release, but other sites for DAG action are also possible." [Abstract]

Scholze, Petra, Zwach, Julia, Kattinger, Alexandra, Pifl, Christian, Singer, Ernst A., Sitte, Harald H.
Transporter-Mediated Release: A Superfusion Study on Human Embryonic Kidney Cells Stably Expressing the Human Serotonin Transporter
J Pharmacol Exp Ther 2000 293: 870-878
"HEK 293 cells stably expressing the human serotonin transporter (hSERT) were grown on coverslips, preincubated with [(3)H]5-hydroxytryptamine (5-HT), and superfused. Substrates of the hSERT [e.g., p-chloroamphetamine (PCA)], increased the basal efflux of [(3)H]5-HT in a concentration-dependent manner. 5-HT reuptake blockers (e.g., imipramine, paroxetine) also raised [(3)H]5-HT efflux, reaching approximately one-third of the maximal effect of the hSERT substrates. In uptake experiments, both groups of substances inhibited [(3)H]5-HT uptake. Using the low-affinity substrate [(3)H]N-methyl-4-phenylpyridinium (MPP(+)) to label the cells in superfusion experiments, reuptake inhibitors failed to enhance efflux. Similar results were obtained using human placental choriocarcinoma (JAR) cells that constitutively express the hSERT at a low level. By contrast, PCA raised [(3)H]MPP(+) efflux in both types of cells, and its effect was inhibited by paroxetine. The addition of the Na(+),K(+)-ATPase inhibitor ouabain (100 microM) to the superfusion buffer enhanced basal efflux of [(3)H]5-HT-loaded hSERT cells by approximately 2-fold; the effect of PCA (10 microM) was strongly augmented by ouabain, whereas the effect of imipramine was not. The Na(+)/H(+) ionophore monensin (10 microM) also augmented the effect of PCA on efflux of [(3)H]5-HT as well as on efflux of [(3)H]MPP(+). In [(3)H]5-HT-labeled cells, the combination of imipramine and monensin raised [(3)H]5-HT efflux to a greater extent than either of the two substances alone. In [(3)H]MPP(+)-labeled cells, imipramine had no effect on its own and fully reversed the effect of monensin. The results suggest that the [(3)H]5-HT efflux caused by uptake inhibitors is entirely due to interrupted high-affinity reuptake, which is ongoing even under superfusion conditions." [Full Text]

Zahniser NR, Doolen S.
Chronic and acute regulation of Na+/Cl- -dependent neurotransmitter transporters: drugs, substrates, presynaptic receptors, and signaling systems.
Pharmacol Ther 2001 Oct;92(1):21-55
"Na+/Cl- -dependent neurotransmitter transporters, which constitute a gene superfamily, are crucial for limiting neurotransmitter activity. Thus, it is critical to understand their regulation. This review focuses primarily on the norepinephrine transporter, the dopamine transporter, the serotonin transporter, and the gamma-aminobutyric acid transporter GAT1. Chronic administration of drugs that alter neurotransmitter release or inhibit transporter activity can produce persistent compensatory changes in brain transporter number and activity. However, regulation has not been universally observed. Transient alterations in norepinephrine transporter, dopamine transporter, serotonin transporter, and GAT1 function and/or number occur in response to more acute manipulations, including membrane potential changes, substrate exposure, ethanol exposure, and presynaptic receptor activation/inhibition. In many cases, acute regulation has been shown to result from a rapid redistribution of the transporter between the cell surface and intracellular sites. Second messenger systems involved in this rapid regulation include protein kinases and phosphatases, of which protein kinase C has been the best characterized. These signaling systems share the common characteristic of altering maximal transport velocity and/or cell surface expression, consistent with regulation of transporter trafficking. Although less well characterized, arachidonic acid, reactive oxygen species, and nitric oxide also alter transporter function. In addition to post-translational modifications, cytoskeleton interactions and transporter oligomerization regulate transporter activity and trafficking. Furthermore, promoter regions involved in transporter transcriptional regulation have begun to be identified. Together, these findings suggest that Na+/Cl- -dependent neurotransmitter transporters are regulated both long-term and in a more dynamic manner, thereby providing several distinct mechanisms for altering synaptic neurotransmitter concentrations and neurotransmission." [Abstract]

Sandoval, Veronica, Riddle, Evan L., Ugarte, Yvette V., Hanson, Glen R., Fleckenstein, Annette E.
Methamphetamine-Induced Rapid and Reversible Changes in Dopamine Transporter Function: An In Vitro Model
J. Neurosci. 2001 21: 1413-1419
"This laboratory has demonstrated that a single methamphetamine (METH) injection rapidly and reversibly decreases the activity of the dopamine transporter (DAT), as assessed ex vivo in synaptosomes prepared from treated rats. This decrease does not occur because of residual drug introduced by the original injection or nor is it associated with a change in binding of the DAT ligand WIN35428. The purpose of this study was to elucidate the mechanism or mechanisms of this METH effect by determining whether direct application of this stimulant to synaptosomes causes changes in DAT similar to those observed ex vivo. Similar to the ex vivo effect, incubation of striatal synaptosomes with METH decreased DAT activity, but not WIN35428 binding: the effect on activity was not eliminated by repeated washing of synaptosomes. Also, as observed ex vivo, incubation with 3,4-methylenedioxymethamphetamine, but not cocaine or methylphenidate, caused a METH-like reduction in DAT function. The rapid and reversible METH-induced diminution in DAT activity did not occur because of a change in membrane potential, as assessed in vitro and ex vivo by [3H]tetraphenylphosphonium accumulation. However, the METH-related decline in DAT function may be attributed to phosphorylation because NPC15437, a protein kinase C inhibitor, attenuated the METH-induced decline in DAT function. Similarities between previously reported effects ex vivo of a single METH injection on serotonin and norepinephrine transporter function and effects of direct METH application in vitro were also found. Together, these data demonstrate that the in vitro incubation model mimics the rapid and reversible effects observed after a single METH injection." [Full Text]

Gulley JM, Doolen S, Zahniser NR.
Brief, repeated exposure to substrates down-regulates dopamine transporter function in Xenopus oocytes in vitro and rat dorsal striatum in vivo.
J Neurochem 2002 Oct;83(2):400-11
"In heterologous expression systems, dopamine transporter (DAT) cell-surface localization is reduced after relatively prolonged exposure to d-amphetamine (AMPH) or dopamine (DA), suggesting a role for substrate-mediated regulation of transporter function. Here, we investigated whether brief, repeated periods of substrate exposure modulated transporter function, first, in an in vitro model system and, second, in intact rat brain. In human DAT-expressing Xenopus laevis oocytes, repeated exposure to low micromolar concentrations of DA, AMPH or tyramine markedly reduced transport-mediated currents. This functional down-regulation was attenuated by inclusion of a protein kinase C (PKC) inhibitor and probably reflects DAT redistribution, as cell-surface [3H]WIN 35 428 binding was significantly lower following DA exposure. High-speed chronoamperometry was used to measure clearance of exogenously applied DA in dorsal striatum (STR) and nucleus accumbens (NAc) of anesthetized rats. In STR, frequent (every 2 min) applications of DA altered DA clearance parameters in a manner consistent with profound down-regulation of DAT function. Similar changes were not observed in NAc or after repeated vehicle (ascorbic acid) application. Together, our results suggest that brief, repeated periods of substrate exposure lead to rapid down-regulation of DAT activity and that this type of regulation can occur in vivo in STR, but not NAc." [Abstract]

Crespi D, Mennini T, Gobbi M.
Carrier-dependent and Ca(2+)-dependent 5-HT and dopamine release induced by (+)-amphetamine, 3,4-methylendioxymethamphetamine, p-chloroamphetamine and (+)-fenfluramine.
Br J Pharmacol 1997 Aug;121(8):1735-43
"1. The mechanism underlying 5-hydroxytryptamine (5-HT) and/or dopamine release induced by (+)-amphetamine ((+)-Amph), 3,4-methylendioxymethamphetamine (MDMA), p-chloroamphetamine (pCA) and (+)-fenfluramine ((+)-Fen) was investigated in rat brain superfused synaptosomes preloaded with the 3H neurotransmitters. 2. Their rank order of potency for [3H]-5-HT-releasing activity was the same as for inhibition of 5-HT uptake (pCA > or = MDMA > or = (+)-Fen > > (+)-Amph). Similarly, their rank order as [3H]-dopamine releasers and dopamine uptake inhibitors was the same ((+)-Amph > > pCA = MDMA > > (+)-Fen). We also confirmed that the release induced by these compounds was prevented by selective transporter inhibitors (indalpine or nomifensine). 3. [3H]-5HT and/or [3H]-dopamine release induced by all these compounds was partially (31-80%), but significantly Ca(2+)-dependent. Lack of extracellular Ca2+ did not alter uptake mechanisms nor did it modify the carrier-dependent dopamine-induced [3H]-dopamine release. (+)-Amph-induced [3H]-dopamine release and pCA- and MDMA-induced [3H]-5-HT release were significantly inhibited by omega-agatoxin-IVA, a specific blocker of P-type voltage-operated Ca(2+)-channels, similar to the previous results on (+)-Fen-induced [3H]-5-HT release. 4. Methiothepin inhibited the Ca(2+)-dependent component of (+)-Amph-induced [3H]-dopamine release with high potency (70 nM), as previously found with (+)-Fen-induced [3H]-5-HT release. The inhibitory effect of methiothepin was not due to its effects as a transporter inhibitor or Ca(2+)-channel blocker and is unlikely to be due to its antagonist properties on 5-HT1/2, dopamine or any other extracellular receptor. 5. These results indicate that the release induced by these compounds is both 'carrier-mediated' and Ca(2+)-dependent (possibly exocytotic-like), with the specific carrier allowing the amphetamines to enter the synaptosome. The Ca(2+)-dependent release is mediated by Ca(2+)-influx (mainly through P-type Ca(2+)-channels), possibly triggered by the drug interacting with an unknown intracellular target, affected by methiothepin, common to both 5-HT and dopamine synaptosomes." [Abstract]

Fournier F, Charnet P, Bourinet E, Vilbert C, Matifat F, Charpentier G, Navarre P, Brule G, Marlot D.
Regulation by protein kinase-C of putative P-type Ca channels expressed in Xenopus oocytes from cerebellar mRNA.
FEBS Lett 1993 Feb 8;317(1-2):118-24
"Xenopus oocytes injected with rat cerebellar mRNA expressed functional voltage-dependent Ca channels detected as an inward Ba current (IBa). The pharmacological resistance to dihydropyridines and omega-conotoxin together with the blockade obtained with Agelenopsis aperta venom suggest that these channels could be somehow assimilated to P-type Ca channels. The precise nature of the transplanted Ca channels was assessed by hybrid-arrest experiments using a specific oligonucleotide antisense-derivated from the recently cloned alpha 1-subunit of P channels (BI-1 clone). In addition, we demonstrate that exogenous Ca channel activity was enhanced by two different PKC activators (a phorbol ester and a structural analog to diacylglycerol). The general electrophysiological and pharmacological properties of the stimulated Ca channels remain unchanged. This potentiation induced by PKC activators is antagonized by a PKC inhibitor (staurosporine) and by a monoclonal antibody directed against PKC. It is concluded that P-type Ca channels are potentially regulated by PKC phosphorylation and the functional relevance of this intracellular pathway is discussed." [Abstract]

Kimura M, Yamanishi Y, Hanada T, Kagaya T, Kuwada M, Watanabe T, Katayama K, Nishizawa Y.
Involvement of P-type calcium channels in high potassium-elicited release of neurotransmitters from rat brain slices.
Neuroscience 1995 Jun;66(3):609-15
"Several types of voltage-dependent calcium channels appear to occur in neurons, although coupling of the particular subtype of calcium channels to the release of neurotransmitter has not been clearly understood. We have examined the effects of subtype-specific inhibitors of the calcium channels on depolarization-induced release of endogenous neurotransmitters from brain slices. High potassium-induced release of glutamate and aspartate from hippocampal and striatal slices was almost completely inhibited by a P-type channel blocker, omega-agatoxin IVA. omega-Agatoxin IVA also completely inhibited the release of serotonin from the hippocampal slices with almost the same potency as in the case of glutamate, whereas the potency in blocking the release of serotonin and dopamine from striatal slices was lower than that from the hippocampal slices. Another calcium channel blocker, omega-agatoxin TK, that was recently found to block P-type channels with very similar selectivity and potency to omega-agatoxin IVA, also inhibited the release of amino acid transmitters and monoamines, though its potency was lower than that of omega-agatoxin IVA. An N-type channel blocker, omega-conotoxin GVIA, partially inhibited the neurotransmitter release, but an L-type channel blocker, nifedipine was ineffective. We propose that the activation of P-type calcium channels makes a major contribution to depolarization-elicited neurotransmitter release in the CNS and that multiple P-type channels sensitive to omega-agatoxin IVA and omega-agatoxin TK modulate the neurotransmitter release." [Abstract]

Dobrev D, Milde AS, Andreas K, Ravens U.
The effects of verapamil and diltiazem on N-, P- and Q-type calcium channels mediating dopamine release in rat striatum.
Br J Pharmacol 1999 May;127(2):576-82
"1. The putative inhibitory effects of verapamil and diltiazem on neuronal non-L-type Ca2+ channels were studied by investigating their effects on either K+- or veratridine-evoked [3H]-dopamine ([3H]-DA) release in rat striatal slices. Involvement of N-, P- and Q-type channels was identified by sensitivity of [3H]-DA release to omega-conotoxin GVIA (omega-CTx-GVIA), omega-agatoxin IVA (omega-Aga-IVA) and omega-conotoxin MVIIC (omega-CTx-MVIIC), respectively. 2. KCl (50 mM)-evoked [3H]-DA release was abolished in the absence of Ca2+, and was insensitive to dihydropyridines (up to 30 microM). It was significantly blocked by omega-CTx-GVIA (1 microM), omega-Aga-IVA (30 nM) and was confirmed to be abolished by omega-CTx-MVIIC (3 microM), indicating involvement of N-, P- and Q-type channel subtypes. 3. Verapamil and diltiazem inhibited K+-evoked [3H]-DA release in a concentration-dependent manner. The inhibitory effects of verapamil or diltiazem (each 30 microM) were fully additive to the effect of omega-CTx-GVIA (1 microM), whereas co-application with omega-Aga-IVA (30 nM) produced similar effects to those of omega-Aga-IVA alone. 4. As shown previously, veratridine-evoked [3H]-DA release in Ca2+ containing medium exclusively involves Q-type Ca2+ channels. Here, diltiazem (30 microM) did not inhibit veratridine-evoked [3H]-DA release, whereas verapamil (30 microM) partially inhibited it, indicating possible involvement of Q-type channels in verapamil-induced inhibition. However, verapamil (30 microM) inhibited this release even in the absence of extracellular Ca2+, suggesting that Na+ rather than Q-type Ca2+ channels are involved. 5. Taken together, our results suggest that verapamil can block P- and at higher concentrations possibly N- and Q-type Ca2+ channels linked to [3H]-DA release, whereas diltiazem appears to block P-type Ca2+ channels only." [Abstract]

Gnegy ME, Hong P, Ferrell ST.
Phosphorylation of neuromodulin in rat striatum after acute and repeated, intermittent amphetamine.
Brain Res Mol Brain Res 1993 Dec;20(4):289-98
"Repeated, intermittent treatment of rats with amphetamine results in a sensitization of locomotor and stereotyped behaviors that is accompanied by an enhancement in stimulus-induced dopamine release. Increased phosphorylation of the neural specific calmodulin-binding protein, neuromodulin (GAP-43, B-50, F1) has been demonstrated in other forms of synaptic plasticity and plays a role in neurotransmitter release. To determine whether neuromodulin phosphorylation was altered during amphetamine sensitization, the in vivo phosphorylated state of neuromodulin was examined in rat striatum in a post hoc phosphorylation assay. Female, Holtzman rats received saline or 2.5 mg/kg amphetamine twice weekly for 5 weeks. One week after the last dose of amphetamine, rats were challenged with either 1 mg/kg or 2.5 mg/kg amphetamine or saline and the rats were sacrificed 30 min later. Purified synaptic plasma membranes were prepared in the presence of EGTA and okadaic acid to inhibit dephosphorylation, and were subsequently phosphorylated in the presence of purified protein kinase C and [gamma-32P]ATP. The protein kinase C-mediated post hoc phosphorylation of neuromodulin was significantly reduced in groups that received either acute or repeated amphetamine suggesting that neuromodulin in those groups contained more endogenous phosphate. The acute, challenge dose of amphetamine increased neuromodulin phosphorylation in the saline-treated controls but not in the repeated amphetamine-pretreated group. Anti-neuromodulin immunoblots showed no change in neuromodulin levels in any group. There was no significant change in protein kinase C activity in any treatment group. To further investigate the effect of acute amphetamine, the ability of amphetamine to alter neuromodulin phosphorylation in 32Pi-preincubated Percoll-purified rat striatal synaptosomes was examined. Amphetamine (10 microM) significantly increased phosphorylation of a 53 kDa band that migrated with authentic neuromodulin in the synaptosomes by 22% while 500 nM 12-O-tetradecanoylphorbol 13-acetate (TPA) increased neuromodulin phosphorylation by 45%. These data suggest that one injection of amphetamine can increase neuromodulin phosphorylation in rat striatum and that this increase is maintained for at least 1 week following a repeated, sensitizing regimen of amphetamine. Since sensitization can be induced with one dose of amphetamine, it is possible that enhanced neuromodulin phosphorylation could contribute to neurochemical events leading to enhanced release of dopamine and/or behavioral sensitization." [Abstract]

Hens JJ, De Wit M, Dekker LV, Boomsma F, Oestreicher AB, Margolis F, Gispen WH, De Graan PN.
Studies on the role of B-50 (GAP-43) in the mechanism of Ca(2+)-induced noradrenaline release: lack of involvement of protein kinase C after the Ca2+ trigger.
J Neurochem 1993 Apr;60(4):1264-73
"The involvement of B-50, protein kinase C (PKC), and PKC-mediated B-50 phosphorylation in the mechanism of Ca(2+)-induced noradrenaline (NA) release was studied in highly purified rat cerebrocortical synaptosomes permeated with streptolysin-O. Under optimal permeation conditions, 12% of the total NA content (8.9 pmol of NA/mg of synaptosomal protein) was released in a largely (> 60%) ATP-dependent manner as a result of an elevation of the free Ca2+ concentration from 10(-8) to 10(-5) M Ca2+. The Ca2+ sensitivity in the micromolar range is identical for [3H]NA and endogenous NA release, indicating that Ca(2+)-induced [3H]NA release originates from vesicular pools in noradrenergic synaptosomes. Ca(2+)-induced NA release was inhibited by either N- or C-terminal-directed anti-B-50 antibodies, confirming a role of B-50 in the process of exocytosis. In addition, both anti-B-50 antibodies inhibited PKC-mediated B-50 phosphorylation with a similar difference in inhibitory potency as observed for NA release. However, in a number of experiments, evidence was obtained challenging a direct role of PKC and PKC-mediated B-50 phosphorylation in Ca(2+)-induced NA release. PKC pseudosubstrate PKC19-36, which inhibited B-50 phosphorylation (IC50 value, 10(-5) M), failed to inhibit Ca(2+)-induced NA release, even when added before the Ca2+ trigger. Similar results were obtained with PKC inhibitor H-7, whereas polymyxin B inhibited B-50 phosphorylation as well as Ca(2+)-induced NA release. Concerning the Ca2+ sensitivity, we demonstrate that PKC-mediated B-50 phosphorylation is initiated at a slightly higher Ca2+ concentration than NA release. Moreover, phorbol ester-induced PKC down-regulation was not paralleled by a decrease in Ca(2+)-induced NA release from streptolysin-O-permeated synaptosomes. Finally, the Ca(2+)- and phorbol ester-induced NA release was found to be additive, suggesting that they stimulate release through different mechanisms. In summary, we show that B-50 is involved in Ca(2+)-induced NA release from streptolysin-O-permeated synaptosomes. Evidence is presented challenging a role of PKC-mediated B-50 phosphorylation in the mechanism of NA exocytosis after Ca2+ influx. An involvement of PKC or PKC-mediated B-50 phosphorylation before the Ca2+ trigger is not ruled out. We suggest that the degree of B-50 phosphorylation, rather than its phosphorylation after PKC activation itself, is important in the molecular cascade after the Ca2+ influx resulting in exocytosis of NA." [Abstract]

Dekker LV, De Graan PN, Oestreicher AB, Versteeg DH, Gispen WH.
Inhibition of noradrenaline release by antibodies to B-50 (GAP-43).
Nature 1989 Nov 2;342(6245):74-6
"Protein kinase C (PKC) is believed to have a crucial role in synaptic transmitter release and long-term potentiation. An important substrate of PKC in the brain is the neuron-specific presynaptically localized protein B-50 (also termed GAP-43, F1, pp46 or P-57). B-50 has been implicated in the regulation of polyphosphoinositide metabolism and calmodulin binding, and in the mechanisms of neurite outgrowth, long-term potentiation and transmitter release. It is still unknown, however, whether B-50 (and/or its phosphorylation) is essential to any of these processes. Here we report the results of studies in which antibodies to B-50, which interfere with B-50 phosphorylation, were introduced into rat cortical synaptosomes that were permeabilized with streptolysin-O (SL-O). We found that the release of [3H]noradrenaline, induced by increasing the Ca2+ concentration in the buffer, is inhibited completely by the antibodies. These results provide the first demonstration of a causal relationship between the PKC substrate B-50 and the release of neurotransmitter." [Abstract]

Jacocks HM 3rd, Cox BM.
Serotonin-stimulated release of [3H]dopamine via reversal of the dopamine transporter in rat striatum and nucleus accumbens: a comparison with release elicited by potassium, N-methyl-D-aspartic acid, glutamic acid and D-amphetamine.
J Pharmacol Exp Ther 1992 Jul;262(1):356-64
"Release of preloaded radiolabeled dopamine ([3H]DA) elicited by several agents from terminal fields of mesolimbic and nigrostriatal projections in rats was compared. Several similarities between the two areas were observed. For example, potassium, which stimulates release both directly, through altering the potential across the membrane of the dopaminergic neuron, as well as indirectly, presumably by releasing endogenous excitatory neurotransmitters, exhibited some similarities to release stimulated by L-glutamate and N-methyl-D-aspartic acid. These included sensitivity to tetrodotoxin (TTX), Mg++ and Ca++. In contrast, release of [3H]DA stimulated by serotonin (5-HT), like that stimulated by D-amphetamine, depended upon a functional dopamine transport system and was less sensitive to TTX, Mg++ and Ca++. 5-HT-stimulated [3H]DA release in striatum (STR) and nucleus accumbens (NACC) was not modified by antagonists at 5-HT2 or 5-HT3 receptors. Differences were observed in release of [3H]DA from STR and NACC. Elevated potassium (20 mM) released about twice as much [3H]DA from NACC as it did from STR. 5-HT was also able to release more [3H]DA from NACC than from STR. Conversely, D-amphetamine released more [3H]DA from STR than from NACC. TTX increased release stimulated by potassium in STR, but decreased release stimulated by potassium in NACC. These observations suggest that receptor- and non-receptor-mediated mechanisms may contribute to regulation of [3H]DA release in mesolimbic and nigrostriatal areas of the brain. It is possible that endogenous 5-HT in STR or NACC acts as a local regulator of DA release acting via a transport-dependent mechanism." [Abstract]

Yoshihara C, Saito N, Taniyama K, Tanaka C.
Differential localization of four subspecies of protein kinase C in the rat striatum and substantia nigra.
J Neurosci 1991 Mar;11(3):690-700
"The distribution of protein kinase C (PKC) subspecies and their colocalization with neurotransmitters were examined in the rat striatum and substantia nigra (SN), using immunocytochemistry. The alpha- and beta I-PKC immunoreactivies were seen predominantly in the perikarya of the neurons in the striatum and SN. In contrast, the beta II- and gamma-PKC immunoreactivities were abundant in both the perikarya and the neuropils in the striatum and only in the neuropils in the SN. From electron microscopic studies, the alpha- and beta I-PKC immunoreactivities were seen adjacent to the plasma membrane, while the beta II-PKC immunoreactivity was observed in the cytoplasm around the Golgi complex. The gamma-PKC immunoreaction was dense throughout the cytoplasm. The double-staining and lesion studies revealed that the alpha-PKC-immunopositive neurons in the striatum were intrinsic cholinergic neurons, and that most of the alpha-PKC-immunoreactive neurons in the SN were dopaminergic neurons. The beta I-PKC-immunoreactive neurons were intrinsic GABAergic neurons in the striatum. Moreover, most of the beta II- and gamma-PKC-immunoreactive neurons were medium-sized neurons projecting to the SN, and over 90% of GABAergic neurons in the caudate-putamen contained beta II-PKC. The beta II-PKC-immunoreactive neurons showed no gamma-PKC immunoreactivity, and the gamma-PKC-immunoreactive neurons were not beta II-PKC immunoreactive. These findings suggest that alpha-PKC is related to the function of the nigral dopaminergic and the striatal cholinergic neurons, and that the beta I-PKC is involved in the function of the striatal intrinsic GABAergic neurons. The beta II- and gamma-PKC may also modulate a specific neuronal function in the striatonigral system." [Abstract]

Chandler LJ, Leslie SW.
Protein kinase C activation enhances K+-stimulated endogenous dopamine release from rat striatal synaptosomes in the absence of an increase in cytosolic Ca2+.
J Neurochem 1989 Jun;52(6):1905-12
"The possibility that protein kinase C modulates neurotransmitter release in brain was investigated by examining the effects of 12-O-tetradecanoylphorbol 13-acetate (TPA) on Ca2+ transport and endogenous dopamine release from rat striatal synaptosomes. TPA (0.16 and 1.6 microM) significantly increased dopamine release by 24 and 33%, respectively, after a 20-min preincubation with TPA followed by 60 s of depolarization with 30 mM KCl. Depolarization-induced 45Ca2+ uptake, measured simultaneously with dopamine release, was not significantly increased by TPA. Neither 45Ca2+ uptake nor dopamine release was altered under resting conditions. When the time course of K+-stimulated 45Ca2+ uptake and dopamine release was examined, TPA (1.6 microM) enhanced dopamine release after 15, 30, and 60 s, but not 1, 3, or 5 s, of depolarization. A slight increase in 45Ca2+ uptake after 60 s of depolarization was also seen. The addition of 30 mM KCl to synaptosomes which had been preloaded with the Ca2+-sensitive fluorophore fura-2 increased the cytosolic free Ca2+ concentration ([Ca2+]i) from 445 nM to 506 nM after 10 s of depolarization and remained elevated after 60 s. TPA had no effect on [Ca2+]i under depolarizing or resting conditions. Replacing extracellular Ca2+ with 100 microM EGTA reduced K+-stimulated (60 s) endogenous dopamine release by 53% and decreased [Ca2+]i to 120 nM. In Ca2+-free medium, 30 mM KCl did not produce an increase in the [Ca2+]i. TPA (1.6 microM) did not alter the [Ca2+]i under resting or depolarizing conditions, but did increase K+-stimulated dopamine release in Ca2+-free medium." [Abstract]

Chowdhury M, Steardo L, Fillenz M.
Protein kinase C mediates the stimulation by somatostatin of dopamine synthesis in the rat striatum and nucleus accumbens.
Neurosci Lett 1987 Nov 23;82(2):196-200
"In experiments using a synaptosomal preparation from the striatum and nucleus accumbens, somatostatin caused a dose-dependent increase in dopamine synthesis. This increase was additive with that produced by 8-BrcAMP but not with that produced by the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA), and was blocked by the protein kinase C inhibitor polymyxin B (PMB). These findings suggest that stimulation of dopamine synthesis by somatostatin is mediated by activation of protein kinase C." [Abstract]

Browman, KE;Kantor, L;Richardson, S;Badiani, A;Robinson, TE;Gnegy, ME
Injection of the protein kinase C inhibitor Ro31-8220 into the nucleus accumbens attenuates the acute response to amphetamine: tissue and behavioral studies
BRAIN RESEARCH 814: (1-2) 112-119 DEC 14 1998
"The ability of amphetamine to produce heightened locomotor activity is thought to be due to its ability to enhance dopamine release from mesolimbic dopamine neurons. The mechanism by which amphetamine increases dopamine release is not well understood, but is thought to involve exchange diffusion with synaptosomal dopamine through the dopamine transporter. We recently reported that amphetamine-mediated dopamine release in the striatum is also dependent on protein kinase C activity. In the current study, we investigated the role of protein kinase C activity in the acute neurochemical and behavioral response to amphetamine in the nucleus accumbens. Consistent with previous results in the striatum, amphetamine-stimulated dopamine release from nucleus accumbens tissue was inhibited by the specific protein kinase C inhibitor Ro31-8220, but not by the relatively inactive analog bisindoylmaleimide V. Ln addition, the effects of protein kinase C activity on the acute behavioral response to amphetamine was examined by injecting Ro31-8220 into the nucleus accumbens 15 min prior to intra-accumbens amphetamine. Pretreatment with Ro31-8220 attenuated the motor-stimulant effects of intra-accumbens amphetamine relative to control subjects pretreated with vehicle. Bisindoylmaleimide V did not significantly inhibit the motor-stimulant effects of intra-accumbens amphetamine. These results suggest that the action of amphetamine in the nucleus accumbens in increasing dopamine release and locomotor activity is dependent on protein kinase C activity." [Abstract]

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Recent MDMA Pharmacology Research

1) Kousik SM, Napier TC, Carvey PM
The Effects of Psychostimulant Drugs on Blood Brain Barrier Function and Neuroinflammation.
Front Pharmacol. 2012;3:121.
The blood brain barrier (BBB) is a highly dynamic interface between the central nervous system (CNS) and periphery. The BBB is comprised of a number of components and is part of the larger neuro(glio)vascular unit. Current literature suggests that psychostimulant drugs of abuse alter the function of the BBB which likely contributes to the neurotoxicities associated with these drugs. In both preclinical and clinical studies, psychostimulants including methamphetamine, MDMA, cocaine, and nicotine, produce BBB dysfunction through alterations in tight junction protein expression and conformation, increased glial activation, increased enzyme activation related to BBB cytoskeleton remodeling, and induction of neuroinflammatory pathways. These detrimental changes lead to increased permeability of the BBB and subsequent vulnerability of the brain to peripheral toxins. In fact, abuse of these psychostimulants, notably methamphetamine and cocaine, has been shown to increase the invasion of peripheral bacteria and viruses into the brain. Much work in this field has focused on the co-morbidity of psychostimulant abuse and human immunodeficiency virus (HIV) infection. As psychostimulants alter BBB permeability, it is likely that this BBB dysfunction results in increased penetration of the HIV virus into the brain thus increasing the risk of and severity of neuro AIDS. This review will provide an overview of the specific changes in components within the BBB associated with psychostimulant abuse as well as the implications of these changes in exacerbating the neuropathology associated with psychostimulant drugs and HIV co-morbidity. [PubMed Citation] [Order full text from Infotrieve]

2) Majumder I, White JM, Irvine RJ
Antidepressant-like effects of ecstasy in subjects with a predisposition to depression.
Addict Behav. 2012 Oct;37(10):1189-92.
[PubMed Citation] [Order full text from Infotrieve]

3) Hysek CM, Liechti ME
Effects of MDMA alone and after pretreatment with reboxetine, duloxetine, clonidine, carvedilol, and doxazosin on pupillary light reflex.
Psychopharmacology (Berl). 2012 Jun 15;
RATIONALE: Pupillometry can be used to characterize autonomic drug effects. OBJECTIVE: This study was conducted to determine the autonomic effects of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy), administered alone and after pretreatment with reboxetine, duloxetine, clonidine, carvedilol, and doxazosin, on pupillary function. METHODS: Infrared pupillometry was performed in five placebo-controlled randomized studies. Each study included 16 healthy subjects (eight men, eight women) who received placebo-MDMA (125 mg), placebo-placebo, pretreatment-placebo, or pretreatment-MDMA using a crossover design. RESULTS: MDMA produced mydriasis, prolonged the latency, reduced the response to light, and shortened the recovery time. The impaired reflex response was associated with subjective, cardiostimulant, and hyperthermic drug effects and returned to normal within 6 h after MDMA administration when plasma MDMA levels were still high. Mydriasis was associated with changes in plasma MDMA concentration over time and longer-lasting. Both reboxetine and duloxetine interacted with the effects of MDMA on pupillary function. Clonidine did not significantly reduce the mydriatic effects of MDMA, although it produced miosis when administered alone. Carvedilol and doxazosin did not alter the effects of MDMA on pupillary function. CONCLUSIONS: The MDMA-induced prolongation of the latency to and reduction of light-induced miosis indicate indirect central parasympathetic inhibition, and the faster recovery time reflects an increased sympathomimetic action. Both norepinephrine and serotonin mediate the effects of MDMA on pupillary function. Although mydriasis is lasting and mirrors the plasma concentration-time curve of MDMA, the impairment in the reaction to light is associated with the subjective and other autonomic effects of MDMA and exhibits acute tolerance. [PubMed Citation] [Order full text from Infotrieve]

4) Yubero-Lahoz S, Pardo R, Farre M, Mathuna BO, Torrens M, Mustata C, Perez-Mańá C, Langohr K, Carbó ML, de la Torre R
Changes in CYP1A2 activity in humans after 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) administration using caffeine as probe drug.
Drug Metab Pharmacokinet. 2012 May 22;
3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) is a ring-substituted amphetamine widely used for recreational purposes. MDMA is predominantly O-demethylenated in humans by cytochrome P450 (CYP) 2D6, and is also a potent mechanism-based inhibitor of the enzyme. After assessing the inhibition and recovery of CYP2D6 in a previous study, the aim of this work was to study in humans the activity of CYP1A2 in vivo after CYP2D6 had been inhibited by MDMA, using caffeine as a probe drug. Twelve male and nine female recreational MDMA users were included. In session 1, 100 mg of caffeine was given at 0 h. In session 2, a 1.5 mg/kg MDMA dose (range 75-100 mg) was given at 0 h followed by a 100 mg dose of caffeine 4 h later. Aliquots of plasma were assayed for caffeine (137X) and paraxanthine (17X) and statistically significant differences were assessed with a one-way ANOVA. There were significant gender differences at basal condition, which persisted after MDMA administration. CYP1A2 activity was higher in both genders after drug administration, with an increase in 40% in females and 20% in males. Results show an increase in CYP1A2 activity when CYP2D6 is inhibited by MDMA in both genders, being more pronounced in females. [PubMed Citation] [Order full text from Infotrieve]

5) Vanattou-Saďfoudine N, McNamara R, Harkin A
Caffeine provokes adverse interactions with MDMA ("Ecstasy") and related psychostimulants: mechanisms and mediators.
Br J Pharmacol. 2012 Jun 1;
Concomitant consumption of caffeine with recreational psychostimulant drugs of abuse can provoke severe acute adverse reactions in addition to longer term consequences. The mechanisms by which caffeine increases the toxicity of psychostimulants include changes to body temperature regulation, cardiotoxicity and lowering of the seizure threshold. Caffeine also influences the stimulatory, discriminative and reinforcing effects of psychostimulant drugs. In this review we consider our current understanding of such caffeine-related drug interactions, placing a particular emphasis on an adverse interaction between caffeine and the substituted amphetamine, 3,4 methylenedioxymethamphetamine (MDMA; "Ecstasy"), which has been most recently described and characterised. Co-administration of caffeine profoundly enhances the acute toxicity of MDMA in rats, as manifested by high core body temperature, tachycardia and increased mortality. In addition, co-administration of caffeine enhances the long-term serotonergic neurotoxicity induced by MDMA. Observations to date support an interactive model of drug-induced toxicity comprising MDMA related enhancement of dopamine release coupled to a caffeine-mediated antagonism of adenosine receptors in addition to inhibition of phosphodiesterase (PDE). These experiments are reviewed together with reports of caffeine-related drug interactions with cocaine, d-amphetamine and ephedrine where similar mechanisms are implicated. Understanding the underlying mechanisms will guide appropriate intervention strategies for the management of severe reactions and potential for increased drug related toxicity resulting from concomitant caffeine consumption. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society. [PubMed Citation] [Order full text from Infotrieve]

6) Machalova A, Slais K, Vrskova D, Sulcova A
Differential effects of modafinil, methamphetamine, and MDMA on agonistic behavior in male mice.
Pharmacol Biochem Behav. 2012 Aug;102(2):215-23.
The aim of the present study was to compare the behavioral effects of modafinil, an atypical psychostimulatory acting and cognitive-function improving drug, with the effects of the psychostimulants methamphetamine (MET) and MDMA (3,4-methylenedioxymethamphetamine, or "ecstasy") in a model of mouse agonistic behavior. This model enables the observation of ethologically well-defined sociable, timid, aggressive, and locomotor behavioral acts and postures. Singly-housed male mice (isolates) were separated into 4 groups. The observations were performed in 4 sessions, 1week apart. In each interaction, singly-housed mice were paired with non-aggressive group-housed partners for 4min in a neutral environment. The isolates received, in a Latin square design, either a) a vehicle or modafinil at doses 2.0, 10.0, or 50.0mg/kg; or b) a vehicle or MET at doses 1.0, 5.0, or 10.0mg/kg; or c) a vehicle or MDMA at doses 2.5, 10.0, or 30.0mg/kg. The isolates were categorized as timid or aggressive according to their behavior in the control interaction (vehicle pre-treatment). Elements of locomotor, sociable, aggressive, and timid behavior were evaluated (one-way ANOVA). In the aggressive mice, no change in the sum of aggressive behavior was measured following modafinil administration, while both methamphetamine and MDMA produced dose-dependent inhibition of aggression (p<0.01). The substantial difference in the tested drug effects on agonistic behavior was an increased occurrence of sociable acts (p<0.01) accompanied by a simultaneous increase of timid acts (p<0.01) recorded after MDMA, but not after modafinil or methamphetamine administration. In the timid mice, at least some doses of modafinil decreased timidity (p<0.01) and increased aggression (p<0.01) with no effect on sociability. Administration of MDMA increased timid activities (p<0.01). Both MDMA and MET decreased sociability (p<0.01). [PubMed Citation] [Order full text from Infotrieve]

7) Hysek CM, Simmler LD, Nicola VG, Vischer N, Donzelli M, Krähenbühl S, Grouzmann E, Huwyler J, Hoener MC, Liechti ME
Duloxetine inhibits effects of MDMA ("ecstasy") in vitro and in humans in a randomized placebo-controlled laboratory study.
PLoS One. 2012;7(5):e36476.
This study assessed the effects of the serotonin (5-HT) and norepinephrine (NE) transporter inhibitor duloxetine on the effects of 3,4-methylenedioxy-methamphetamine (MDMA, ecstasy) in vitro and in 16 healthy subjects. The clinical study used a double-blind, randomized, placebo-controlled, four-session, crossover design. In vitro, duloxetine blocked the release of both 5-HT and NE by MDMA or by its metabolite 3,4-methylenedioxyamphetamine from transmitter-loaded human cells expressing the 5-HT or NE transporter. In humans, duloxetine inhibited the effects of MDMA including elevations in circulating NE, increases in blood pressure and heart rate, and the subjective drug effects. Duloxetine inhibited the pharmacodynamic response to MDMA despite an increase in duloxetine-associated elevations in plasma MDMA levels. The findings confirm the important role of MDMA-induced 5-HT and NE release in the psychotropic effects of MDMA. Duloxetine may be useful in the treatment of psychostimulant dependence. TRIAL REGISTRATION: NCT00990067. [PubMed Citation] [Order full text from Infotrieve]

8) Rust KY, Baumgartner MR, Dally AM, Kraemer T
Prevalence of new psychoactive substances: A retrospective study in hair.
Drug Test Anal. 2012 Jun;4(6):402-8.
New psychoactive substances are conquering the drug scene. Police seize different colourful packages with exceptional names. They are declared as 'bath salts', 'plant food', or 'research chemical powders'. Little is known about the actual prevalence of these drugs. Reanalysis of hair samples from routine cases concerning the presence of new psychoactive substances or 'smart drugs' should provide insight into changing patterns of designer drugs. All hair samples from 2009 and 2010 that originally tested positive for amphetamines or MDMA (N?=?325) were reanalyzed for new or smart drugs such as 4-fluoroamphetamine, piperazines (BZP, mCPP and TFMPP), cathinones (4-MMC (mephedrone), methylone, butylone, ethylone, MDPV, methcathinone and cathinone), methylphenidate and ketamine. Hair snippets were extracted using a two-step extraction procedure. The analytes were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) (electrospray ionization; multiple-reaction-monitoring mode - information dependent acquisition - enhanced product ion scan). New psychoactive substances were found in 120 cases (37%). Concerning the piperazine drugs, mCPP was positive in 34 (10.5%) cases and TFMPP in one case. Five mCPP cases were also positive for trazodone, an antidepressant which is metabolized to mCPP. In 11 (3%) cases, 4-MMC was detected. Concerning the smart drugs, methylphenidate was found in 16 (5%). Ketamine was found in 45 (14%) cases. 4-Fluoroamphetamine was identified in 12 (4%) cases and methylone in one case.In conclusion, there is a high prevalence of these drugs. Consequently, at least the most common ones (e.g. mCPP, KET, 4-MMC and 4-FA) should be included in screening procedures in clinical and forensic toxicology. Copyright © 2012 John Wiley & Sons, Ltd. [PubMed Citation] [Order full text from Infotrieve]

9) López-Arnau R, Martínez-Clemente J, Pubill D, Escubedo E, Camarasa J
Comparative neuropharmacology of three psychostimulant cathinone derivatives: butylone, mephedrone and methylone.
Br J Pharmacol. 2012 Apr 18;
Background and purpose:? In the present study we compare the neurochemical profile of three new cathinones, butylone, mephedrone and methylone, as regards their potential to inhibit plasmalemmal and vesicular monoamine transporters. Their interaction with 5-HT and DA receptors and their psychostimulant effect was also studied. Experimental approach:? Locomotor activity was recorded in mice following different doses of cathinones. Monoamine uptake assays were performed in rat purified synaptosomes. Radioligand binding assays were carried out to assess the affinity of these compounds for monoamine transporters or receptors. Key results:? Butylone, mephedrone and methylone (5-25 mg Kg(-1) ) caused hyperlocomotion which was prevented with ketanserin or haloperidol. Methylone was the most potent compound inhibiting both [(3) H]5-HT and [(3) H]DA uptake with IC(50 ) values that correlate with its affinity for DA and 5-HT transporter. Mephedrone was found to be the cathinone derivative with most affinity for VMAT-2 causing the inhibition of DA uptake. The affinity of cathinones for 5-HT(2A) receptors was similar to that of MDMA. Conclusions and implications:? Butylone and methylone induce hyperlocomotion through an activation of 5-HT(2A) receptors and an increase in extracellular DA. They inhibit 5-HT and DA uptake competing with the substrate. Methylone is the most potent 5-HT and DA uptake inhibitor and its effect partially persists after withdrawal. Mephedrone-induced hyperlocomotion is dependent on endogenous 5-HT. Vesicular content plays a key role in the effect of mephedrone, especially in the 5-HT uptake inhibition. Its potency inhibiting NA uptake, leads us to the hypothesis of a sympathetic effect of this cathinone. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society. [PubMed Citation] [Order full text from Infotrieve]

10) Rácz J, Csák R, Faragó R, Vadász V
[The phenomenon of drug change in the interviews with injecting drug users].
Psychiatr Hung. 2012;27(1):29-47.
[PubMed Citation] [Order full text from Infotrieve]

11) Papaseit E, Vázquez A, Pérez-Mańá C, Pujadas M, de la Torre R, Farré M, Nolla J
Surviving life-threatening MDMA (3,4-methylenedioxymethamphetamine, ecstasy) toxicity caused by ritonavir (RTV).
Intensive Care Med. 2012 Jul;38(7):1239-40.
[PubMed Citation] [Order full text from Infotrieve]

12) Stankevicius D, Ferraz-de-Paula V, Ribeiro A, Pinheiro ML, Ligeiro de Oliveira AP, Damazo AS, Lapachinske SF, Moreau RL, Tavares de Lima W, Palermo-Neto J
3,4-methylenedioxymethamphetamine (ecstasy) decreases inflammation and airway reactivity in a murine model of asthma.
Neuroimmunomodulation. 2012;19(4):209-19.
[PubMed Citation] [Order full text from Infotrieve]

13) Hysek C, Schmid Y, Rickli A, Simmler L, Donzelli M, Grouzmann E, Liechti M
Carvedilol inhibits the cardiostimulant and thermogenic effects of MDMA in humans.
Br J Pharmacol. 2012 Aug;166(8):2277-88.
BACKGROUND AND PURPOSE The use of ±3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') is associated with cardiovascular complications and hyperthermia. EXPERIMENTAL APPROACH We assessed the effects of the ?(1) - and ?-adrenoceptor antagonist carvedilol on the cardiostimulant, thermogenic and subjective responses to MDMA in 16 healthy subjects. Carvedilol (50?mg) or placebo was administered 1?h before MDMA (125?mg) or placebo using a randomized, double-blind, placebo-controlled, four-period crossover design. KEY RESULTS Carvedilol reduced MDMA-induced elevations in blood pressure, heart rate and body temperature. Carvedilol did not affect the subjective effects of MDMA including MDMA-induced good drug effects, drug high, drug liking, stimulation or adverse effects. Carvedilol did not alter the plasma exposure to MDMA. CONCLUSIONS AND IMPLICATIONS ?(1) - and ?-Adrenoceptors contribute to the cardiostimulant and thermogenic effects of MDMA in humans but not to its psychotropic effects. Carvedilol could be useful in the treatment of cardiovascular and hyperthermic complications associated with ecstasy use. [PubMed Citation] [Order full text from Infotrieve]

14) Murray E, Bruno R, Brown J
Residual effects of ecstasy (3,4-methylenedioxymethamphetamine) on low level visual processes.
Hum Psychopharmacol. 2012 Mar;27(2):226-34.
'Ecstasy' (3,4-methylenedioxymethamphetamine) induces impaired functioning in the serotonergic system, including the occipital lobe. This study employed the 'tilt aftereffect' paradigm to operationalise the function of orientation-selective neurons among ecstasy consumers and controls as a means of investigating the role of reduced serotonin on visual orientation processing. The magnitude of the tilt aftereffect reflects the extent of lateral inhibition between orientation-selective neurons and is elicited to both 'real' contours, processed in visual cortex area V1, and illusory contours, processed in V2. The magnitude of tilt aftereffect to both contour types was examined among 19 ecstasy users (6 ecstasy only; 13 ecstasy-plus-cannabis users) and 23 matched controls (9 cannabis-only users; 14 drug-naive). Ecstasy users had a significantly greater tilt magnitude than non-users for real contours (Hedge's g = 0.63) but not for illusory contours (g = 0.20). These findings provide support for literature suggesting that residual effects of ecstasy (and reduced serotonin) impairs lateral inhibition between orientation-selective neurons in V1, which however suggests that ecstasy may not substantially affect this process in V2. Multiple studies have now demonstrated ecstasy-related deficits on basic visual functions, including orientation and motion processing. Such low-level effects may contribute to the impact of ecstasy use on neuropsychological tests of visuospatial function. [PubMed Citation] [Order full text from Infotrieve]

15) Wetherell MA, Atherton K, Grainger J, Brosnan R, Scholey AB
The effects of multitasking on psychological stress reactivity in recreational users of cannabis and MDMA.
Hum Psychopharmacol. 2012 Mar;27(2):167-76.
[PubMed Citation] [Order full text from Infotrieve]

16) Murphy PN, Bruno R, Ryland I, Wareing M, Fisk JE, Montgomery C, Hilton J
The effects of 'ecstasy' (MDMA) on visuospatial memory performance: findings from a systematic review with meta-analyses.
Hum Psychopharmacol. 2012 Mar;27(2):113-38.
To review, with meta-analyses where appropriate, performance differences between ecstasy (3,4-methylenedioxymethamphetamine) users and non-users on a wider range of visuospatial tasks than previously reviewed. Such tasks have been shown to draw upon working memory executive resources. Abstract databases were searched using the United Kingdom National Health Service Evidence Health Information Resource. Inclusion criteria were publication in English language peer-reviewed journals and the reporting of new findings regarding human ecstasy-users' performance on visuospatial tasks. Data extracted included specific task requirements to provide a basis for meta-analyses for categories of tasks with similar requirements. Fifty-two studies were identified for review, although not all were suitable for meta-analysis. Significant weighted mean effect sizes indicating poorer performance by ecstasy users compared with matched controls were found for tasks requiring recall of spatial stimulus elements, recognition of figures and production/reproduction of figures. There was no evidence of a linear relationship between estimated ecstasy consumption and effect sizes. Given the networked nature of processing for spatial and non-spatial visual information, future scanning and imaging studies should focus on brain activation differences between ecstasy users and non-users in the context of specific tasks to facilitate identification of loci of potentially compromised activity in users. [PubMed Citation] [Order full text from Infotrieve]

17) Parrott AC, Murphy P, Scholey AB
Applied human psychopharmacology: the practical psychobiological consequences of some novel and ancient psychoactive drugs.
Hum Psychopharmacol. 2012 Mar;27(2):103-5.
[PubMed Citation] [Order full text from Infotrieve]

18) Montastruc F, Montastruc G, Vigreux P, Bruneval P, Guilbeau-Frugier C, Cron C, Bagheri H, Delisle B, Lapeyre-Mestre M, Pathak A, Montastruc JL
Valvular Heart Disease in a patient taking 3,4-Methylenedioxymethamphetamine (MDMA, "Ecstasy").
Br J Clin Pharmacol. 2012 Feb 24;
© 2012 The Authors. British Journal of Clinical Pharmacology © 2012 The British Pharmacological Society. [PubMed Citation] [Order full text from Infotrieve]

19) Santoro PE, Nardis ID, Fronterrč P, Felli M, Martello S, Bergamaschi A, Chiarotti M
A snapshot of workplace drug testing in Italy.
Drug Test Anal. 2012 Feb;4(2):66-70.
The Italian Decree on Health and Safety at Work (81/08) prescribes mandatory drug tests for jobs which pose safety hazards to others. Workplace drug testing is performed in accordance with the Provision of the Government-Regions Conference, 2008. The aim of our survey was to examine the prevalence of drug use and the main drug findings in a sample of Italian workers performing hazardous jobs. From September 2009 to February 2011, 551 urine samples were collected in 42 Italian companies. Sample collection was carried out at the workplace by qualified laboratory personnel sent from the Institute of Occupational Medicine of the Catholic University (UCSC) of Rome. The workers to be tested were informed the day before, as the law requires. The samples were checked for adulteration, coded, and sent immediately to the laboratory of the UCSC Forensic Toxicology Analytical Unit. The screening test was an immunoassay. The positive samples proceeded to the confirmatory analysis with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The urine samples were analyzed for cannabis, opiates, amphetamines, methamphetamines, cocaine, methadone, and MDMA. Out of 16 samples .9% screened positive; only 4 of them (0.7%) were confirmed with the LC-MS/MS. Confirmed results included cocaine (2 samples), cannabis (1 sample), both cocaine and cannabis (1 sample). The prevalence of positive samples was lower than expected. Such finding cannot be explained by a low reliability of the testing procedure but could be due to test scheduling. More positive cases might be found performing short-notice random testing. [PubMed Citation] [Order full text from Infotrieve]

20) Rusyniak DE, Zaretsky DV, Zaretskaia MV, Durant PJ, Dimicco JA
The orexin-1 receptor antagonist SB-334867 decreases sympathetic responses to a moderate dose of methamphetamine and stress.
Physiol Behav. 2012 Feb 14;
We recently discovered that inhibiting neurons in the dorsomedial hypothalamus (DMH) attenuated hyperthermia, tachycardia, hypertension, and hyperactivity evoked by the substituted amphetamine 3, 4-methylenedioxymethamphetamine (MDMA). Neurons that synthesize orexin are also found in the region of the DMH. As orexin and its receptors are involved in the regulation of heart rate and temperature, they would seem to be logical candidates as mediators of the effects evoked by amphetamines. The goal of this study was to determine if blockade of orexin-1 receptors in conscious rats would suppress cardiovascular and thermogenic responses evoked by a range of methamphetamine (METH) doses. Male Sprague-Dawley rats (n=6 per group) were implanted with telemetric transmitters measuring body temperature, heart rate, and mean arterial pressure. Animals were randomized to receive pretreatment with either the orexin-1 receptor antagonist SB-334867 (10mg/kg) or an equal volume of vehicle. Thirty minutes later animals were given intraperitoneal (i.p.) injections of either saline, a low (1mg/kg), moderate (5mg/kg) or high (10mg/kg) dose of METH. Pretreatment with SB-334867 significantly attenuated increases in body temperature and mean arterial pressure evoked by the moderate but not the low or high dose of METH. Furthermore, animals treated with SB-334867, compared to vehicle, had lower temperature and heart rate increases after the stress of an i.p. injection. In conclusion, temperature and cardiovascular responses to a moderate dose of METH and to stress appear to involve orexin-1 receptors. The failure to affect a low and a high dose of METH suggests a complex pharmacology dependent on dose. A better understanding of this may lead to the knowledge of how monoamines influence the orexin system and vice versa. [PubMed Citation] [Order full text from Infotrieve]