Tepper SJ, Rapoport A, Sheftell F.
The pathophysiology of migraine.
Neurolog. 2001 Sep;7(5):279-86.
"BACKGROUND: Migraine results from episodic changes in central nervous system physiologic function in hyperexcitable brain manifested by abnormal energy metabolism, lowered threshold for phosphene generation, and increased contingent negative variation. Human functional magnetic resonance imaging and magnetoencepholography data strongly suggest that aura is caused by cortical spreading depression. REVIEW SUMMARY: Brain hyperexcitability may be caused by low magnesium levels, mitochondrial abnormalities with abnormal phosphorylation of adenosine 5'-diphosphate, a dysfunction related to nitric oxide, or calcium channelopathy. Low magnesium can result in opening of calcium channels, increased intracellular calcium, glutamate release, and increased extracellular potassium, which may in turn trigger cortical spreading depression. Mitochondrial dysfunction has been suggested by a low phosphocreatine:Pi ratio and a possible response by migraine patients to riboflavin prophylaxis. Nitroglycerine administration results in a delayed migraine-like headache in migraine patients but not in control patients, and a nonspecific nitric oxide synthase inhibitor aborted migraine at 2 hours in the majority of tested migraine patients compared to controls. Many patients with familial hemiplegic migraine have a missense mutation in the P/Q calcium channel, so that this form of migraine, at least, is associated with a demonstrable calcium channelopathy. CONCLUSIONS: The generation of migraine occurs centrally in the brain stem, sometimes preceded by cortical spreading depression and aura. Activation of the trigeminovascular system stimulates perivascular trigeminal sensory afferent nerves with release of vasoactive neuropeptides, resulting in vasodilation and transduction of central nociceptive information. There is then a relay of pain impulses to central second- and third-order neurons and activation of brain stem autonomic nuclei to induce associated symptoms." [Abstract]

Ashina M.
Nitric oxide synthase inhibitors for the treatment of chronic tension-type headache.
Expert Opin Pharmacother. 2002 Apr;3(4):395-9.
"Chronic tension-type headache may be caused by prolonged painful input from pericranial myofacial tissues, for example tender points, resulting in central sensitisation (increased excitability of neurons in the central nervous system). Animal studies have shown that sensitisation of pain pathways may be caused by or associated with the activation of neuronal nitric oxide synthase and the generation of nitric oxide. Furthermore, it has been shown that nitric oxide synthase inhibitors reduce central sensitisation in animal models of persistent pain. On the basis of this information, the analgesic effect of the nitric oxide synthase inhibitor L-N(G) methyl arginine hydrochloride was investigated. This drug significantly reduced headache and myofacial factors in patients with chronic tension-type headache. These studies show that nitric oxide plays a crucial role in the pathophysiology of tension-type headache. The analgesic effect of nitric oxide synthase inhibition in patients with chronic tension-type headache is probably due to a reduction in central sensitisation at the level of the spinal dorsal horn, trigeminal nucleus or both. Furthermore, inhibition of nitric oxide synthase may become a novel principle in the future treatment of chronic headache." [Abstract]

Thomsen LL, Olesen J.
Nitric oxide in primary headaches.
Curr Opin Neurol. 2001 Jun;14(3):315-21.
"The molecular mechanisms that underlie the primary headaches-migraine, cluster headache and tension-type headache-have not yet been clarified. On the basis of studies in headache induced by intravenous infusions of glyceryl trinitrate (an exogenous nitric oxide donor) and histamine (which liberates nitric oxide from vascular endothelium), it has been suggested that nitric oxide is a likely candidate responsible molecule. The present review deals with the biology of this small messenger molecule, and the updated scientific evidence that suggests a key role for this molecule in primary headaches. This evidence suggests that the release of nitric oxide from blood vessels, perivascular nerve endings or from brain tissue is an important molecular trigger mechanism in spontaneous headache pain. Pilot trials have shown efficacy of a nitric oxide synthase inhibitor in both migraine attacks and chronic tension-type headache. These observations suggest new approaches to the pharmacological treatment of headache." [Abstract]

Read SJ, Smith MI, Hunter AJ, Parsons AA.
Enhanced nitric oxide release during cortical spreading depression following infusion of glyceryl trinitrate in the anaesthetized cat.
Cephalalgia. 1997 May;17(3):159-65.
"Intravenous infusion of glyceryl trinitrate (GTN) into migraineurs induces an immediate headache followed by migraine. We studied the effect of GTN (0.25 microgram kg-1 min-1) on local cerebrovascular laser Doppler flux (rCBFLDF), artery diameter and NO concentration (selective NO microelectrode) in the pial middle cerebral artery perfusion territory of the anaesthetized cat, at rest and during cortical spreading depression (SD). GTN infusion induced a significant increase in pial artery diameter, rCBFLDF, and NO concentration. Following termination of infusion, NO concentrations remained significantly elevated above controls for 60 min, other parameters returned to baseline within 10 min (p < 0.05, ANOVA, post hoc Dunnett's multiple comparison procedure). Two hours after termination of infusion KCl-evoked SD was initiated. GTN-treated animals exhibited significantly (p < 0.05, Kruskal-Wallis) elevated SD-induced NO release compared to controls. All other parameters remained unaffected. Our results demonstrate that GTN induces a prolonged increase in local NO concentrations and enhances SD-induced NO release." [Abstract]

Wahl M, Schilling L, Parsons AA, Kaumann A.
Involvement of calcitonin gene-related peptide (CGRP) and nitric oxide (NO) in the pial artery dilatation elicited by cortical spreading depression.
Brain Res. 1994 Feb 21;637(1-2):204-10.
"The aim of the present study was to examine whether the initial transient arterial dilatation during cortical spreading depression (CSD) was mediated by the release of calcitonin gene-related peptide (CGRP) and/or nitric oxide (NO). This question is of interest as the initial phase of CSD appears to be a model of events occurring during functional hyperemia and during the first period of classic migraine. Using an open cranial window technique, pial arterial diameter in the parietal cortex of cats was recorded with an image splitting method. Employing micropuncture technique, perivascularly applied CGRP8-37 did not alter the resting diameter of pial arteries but antagonized concentration dependently (5 x 10(-9)-10(-6) M) the dilatation (35%) due to 5 x 10(-8) M CGRP. NG-Nitro-L-Arginine (NOLAG, 10(-4) M) also had no effect on resting diameter of pial arteries, indicating that their resting tone is neither mediated by a continuous release of CGRP nor of NO. CSD was triggered by a remote intracortical injection of KCl (150 mM) and recorded by a microelectrode placed adjacent to the artery under investigation. CSD elicited a transient negative DC shift which was accompanied by a peak dilatation of 44 +/- 5.2% (S.E.M.). This dilatation was reduced by approximately 50% during topical application of 10(-7) M CGRP8-37 and 10(-4) M NOLAG each. A 75% inhibition of the CSD-induced dilatation was found during simultaneous application of both compounds. These data indicate that the initial dilatation during CSD is mediated, at least in part, by a release of CGRP and NO." [Abstract]

Obrenovitch TP, Urenjak J, Wang M.
Nitric oxide formation during cortical spreading depression is critical for rapid subsequent recovery of ionic homeostasis.
J Cereb Blood Flow Metab. 2002 Jun;22(6):680-8.
"Cortical spreading depression (CSD) is a temporary disruption of local ionic homeostasis that propagates slowly across the cerebral cortex. Cortical spreading depression promotes lesion progression in experimental stroke, and may contribute to the initiation of migraine attacks. The purpose of this study was to investigate the roles of the marked increase of nitric oxide (NO) formation that occurs with CSD. Microdialysis electrodes were implanted in the cortex of anesthetized rats to perform the following operations within the same region: (1) elicitation of CSD by perfusion of high K+ medium; (2) recording of CSD elicitation; (3) application of the NO synthase inhibitor, NG-nitro-l-arginine methyl ester (l-NAME); and (4) recording of dialysate pH changes. The primary effect of l-NAME (0.3 to 3.0 mmol/L in the perfusion medium) was a marked widening of individual CSD wave, resulting essentially from a delayed initiation of the repolarization phase. This change was due to NO synthase inhibition because it was not observed with the inactive isomer d-NAME, and was reversed by l-arginine. This effect did not appear to be linked to the suppression of a sustained, NO-mediated vascular change associated with the superposition of NO synthase inhibition on high levels of extracellular K+. The delayed initiation of repolarization with local NO synthase inhibition may reflect the suppression of NO-mediated negative feedback mechanisms acting on neuronal or glial processes involved in CSD genesis. However, the possible abrogation of a very brief, NO-mediated vascular change associated with the early phase of CSD cannot be ruled out." [Abstract]

Wang M, Obrenovitch TP, Urenjak J.
Effects of the nitric oxide donor, DEA/NO on cortical spreading depression.
Neuropharmacology. 2003 Jun;44(7):949-57.
"Cortical spreading depression (CSD) is a transient disruption of local ionic homeostasis that may promote migraine attacks and the progression of stroke lesions. We reported previously that the local inhibition of nitric oxide (NO) synthesis with Nomega-nitro-L-arginine methyl ester (L-NAME) delayed markedly the initiation of the recovery of ionic homeostasis from CSD. Here we describe a novel method for selective, controlled generation of exogenous NO in a functioning brain region. It is based on microdialysis perfusion of the NO donor, 2-(N,N-diethylamino)-diazenolate-2-oxide (DEA/NO). As DEA/NO does not generate NO at alkaline pH, and as the brain has a strong acid-base buffering capacity, DEA/NO was perfused in a medium adjusted at alkaline (but unbuffered) pH. Without DEA/NO, such a microdialysis perfusion medium did not alter CSD. DEA/NO (1, 10 and 100 microM) had little effect on CSD by itself, but it reversed in a concentration-dependent manner the effects of NOS inhibition by 1 mM L-NAME. These data demonstrate that increased formation of endogenous NO associated with CSD is critical for subsequent, rapid recovery of cellular ionic homeostasis. In this case, the molecular targets for NO may be located either on brain cells to suppress mechanisms directly involved in CSD genesis, or on local blood vessels to couple flow to the increased energy demand associated with CSD." [Abstract]

Fabricius M, Akgoren N, Lauritzen M.
Arginine-nitric oxide pathway and cerebrovascular regulation in cortical spreading depression.
Am J Physiol. 1995 Jul;269(1 Pt 2):H23-9.
"Nerve cells release nitric oxide (NO) in response to activation of glutamate receptors of the N-methyl-D-aspartate (NMDA) subtype. We explored the hypothesis that NO influences the changes of cerebral blood flow (CBF) during cortical spreading depression (CSD), which is known to be associated with NMDA receptor activation. CBF was monitored in parietal cortex by laser-Doppler flowmetry in halothane-anesthetized rats. Under control conditions, CSD induced regular changes of CBF, which consisted of four phases: a brief hypoperfusion before the direct current (DC) shift; a marked CBF rise during the DC shift; followed by a smaller, but protracted increase of CBF; and a prolonged CBF reduction (the oligemia). NO synthase inhibition by intravenous and/or topical application of NG-nitro-L-arginine enhanced the brief initial hypoperfusion, but the CBF increases and the oligemia were unchanged. L-Arginine prevented the development of the prolonged oligemia after CSD but had no influence on the marked rise of CBF during CSD. Animals treated with L-arginine recovered the reduced vascular reactivity to hypercapnia after CSD much faster than control rats. Functional denervation of cortical and pial arterioles by tetrodotoxin accentuated the pre-CSD hypoperfusion and the oligemia but did not affect the CBF increases. The results suggest that NO is important for the changes of cerebrovascular regulation following CSD. The observations may have clinical importance, since CBF changes during migraine may be triggered by CSD." [Abstract]

Read SJ, Hirst WD, Upton N, Parsons AA.
Cortical spreading depression produces increased cGMP levels in cortex and brain stem that is inhibited by tonabersat (SB-220453) but not sumatriptan.
Brain Res. 2001 Feb 9;891(1-2):69-77.
"Migraine headache is proposed to be mediated by nitric oxide (NO). Suitable mechanisms for eliciting increases in brain NO concentration in migraineurs have not yet been identified, although, animal models highlight cortical spreading depression (CSD) as a potential candidate. These studies have focused on CSD-associated NO release at highly acute time points (min-hours) and have not employed markers of NO metabolism with direct clinical application e.g. cGMP. The current study evaluated changes in plasma cGMP concentrations 3 h, 24 h and 3 days post-CSD and compared these to cortical and brainstem cGMP concentrations at 3 days. Moreover, this study also examined the effect of sumatriptan, a clinically effective antimigraine agent, and tonabersat (SB-220453) a potential novel antimigraine agent, on any observed changes in cGMP. Following pre-treatment with vehicle (n=3), sumatriptan (300 microg kg(-1) i.v, n=3) or tonabersat (SB-220453 10 mg kg(-1) i.p., n=3), CSD was evoked in anaesthetised rats by a 6-min KCl application to the parietal cortex. In the vehicle-treated group a median of eight depolarisations, were observed. Sumatriptan had no effect on the number of depolarisations, whereas tonabersat significantly reduced the number of events (median=2). No depolarisation events were observed throughout the recording period in the sham group. Following KCl application plasma cGMP concentrations were reduced up to 24 h post-CSD, but not significantly different from sham animals at 3 days. CSD in vehicle-treated animals produced a highly significant elevation in cGMP concentration in the brain stem 3 days after application of KCl. cGMP concentration increased 2.3-fold from 68+/-8 fmol/mg in sham animals (n=3) to 158+/-28 fmol/mg in the vehicle group. This increase in brain stem cGMP was abolished by tonabersat pre-treatment but not by sumatriptan." [Abstract]

Smith MI, Read SJ, Chan WN, Thompson M, Hunter AJ, Upton N, Parsons AA.
Repetitive cortical spreading depression in a gyrencephalic feline brain: inhibition by the novel benzoylamino-benzopyran SB-220453.
Cephalalgia. 2000 Jul;20(6):546-53.
"Transient cortical depolarization is implicated in the pathology of migraine. SB-220453 is a potent anti-convulsant which inhibits neurogenic inflammation and cortical spreading depression (SD)-evoked nitric oxide release via a novel but unknown mechanism. This study further investigates the effects of SB-220453 on generation and propagation of repetitive SD in the anaesthetized cat. Vehicle or SB-220453 1, 3 or 10 mg/kg was administered intraperitoneally 90 min prior to induction of SD in the suprasylvian gyrus (SG). Changes in d.c. potential were recorded in the SG and the adjacent marginal gyrus (MG). In vehicle-treated animals (n = 7), a brief exposure (6 min) to KCl induced a median (25-75% range) number of five (four to six) and three (two to four) depolarizations over a duration of 55 min (32-59 min) and 51 min (34-58 min) in the SG and MG, respectively. SB-220453 produced dose-related inhibition of the number of events and period of repetitive SD activity. SB-220453 also reduced SD-induced repetitive pial vasodilatation but had no effect on resting haemodynamics. However, when SD events were observed in the presence of SB-220453, it had no effect on metabolic coupling. These results show that SB-220453 produces marked inhibition of repetitive SD in the anaesthetized cat. SB-220453 may therefore have therapeutic potential in treatment of SD-like activity in migraine." [Abstract]

Knyihar-Csillik E, Tajti J, Chadaide Z, Csillik B, Vecsei L.
Functional immunohistochemistry of neuropeptides and nitric oxide synthase in the nerve fibers of the supratentorial dura mater in an experimental migraine model.
Microsc Res Tech. 2001 May 1;53(3):193-211.
"The supratentorial cerebral dura of the albino rat is equipped with a rich sensory innervation both in the connective tissue and around blood vessels, which includes nociceptive axons and their terminals; these display intense calcitonin gene-related peptide (CGRP) immunoreactivity. Stereotactic electrical stimulation of the trigeminal (Gasserian) ganglion, regarded as an experimental migraine model, caused marked increase and disintegration of club-like perivascular CGRP-immunopositive nerve endings in the dura mater and induced an apparent increase in the lengths of CGRP-immunoreactive axons. Intravenous administration of sumatriptan or eletriptan, prior to electrical stimulation, prevented disintegration of perivascular terminals and induced accumulation of CGRP in terminal and preterminal portions of peripheral sensory axons. Consequently, immunopositive terminals and varicosities increased in size; accumulation of axoplasmic organelles resulted in the "hollow" appearence of numerous varicosities. Since triptans exert their anti-migraine effect by virtue of agonist action on 5-HT(1D/B) receptors, we suggest that these drugs prevent the release of CGRP from perivascular nerve terminals in the dura mater by an action at 5-HT(1D/B) receptors. Nitroglycerine (NitroPOHL), given subcutaneously to rats, induces increased beading of nitric oxide synthase (NOS)-immunoreactive nerve fibers in the supratentorial cerebral dura mater, and an apparent increase in the number of NOS-immunoreactive nerve fibers in the dural areas supplied by the anterior and middle meningeal arteries, and the sinus sagittalis superior. Structural alterations of nitroxidergic axons innervating blood vessels of the dura mater support the idea that nitric oxide (NO) is involved in the induction of headache, a well-known side effect of coronary dilator agents." [Abstract]

Strecker T, Messlinger K.
[Neuropeptide release in the dura mater encephali in response to nitric oxide--relevance for the development of vascular headaches?]
Schmerz. 2003 Jun;17(3):179-84.
"Nitric oxide (NO) and calcitonin gene-related peptide (CGRP), potent vasodilators in the meninges,may be involved in the pathophysiology of vascular headaches such as migraine pain. NO donators can provoke headache attacks in migraineurs and increased levels of CGRP have been found in the venous outflow from the head during migraine attacks. We therefore examined the effect of both NO and CGRP on dural blood, a process which may parallel nociceptive processes in the meninges. 1.Arterial blood flow was measured in the exposed dura mater encephali of the rat using laser Doppler flowmetry. Local application of different NO donors (SNAP,NONOate, and NOC-12) caused dose-dependent increases in meningeal blood flow. CGRP(8-37) at 10(-4) M did not significantly change the basal flow but attenuated increases in blood flow caused by the NO donors at concentrations of 10(-5)-10(-3) M.2. In another series of experiments, the hemisected skulls of adult Wistar rats, complete with intact dura mater, were filled with oxygenated synthetic interstitial fluid (SIF) and the CGRP content of this fluid was assessed every 5 min. When the NO donator NONOate, at concentrations of 10(-5)-10(-3) M, was added to the SIF, or when the SIF was bubbled with NO gas (1000 ppm in N(2) atmosphere) instead of carbogen, CGRP release increased in a concentration-dependent manner. We conclude that the vasodilatory effect of NO that causes increased meningeal blood flow is in part the result of both stimulating the release of CGRP and promoting the vasodilatory action of CGRP. Since NO donors such as nitroglycerin are known to provoke headache and CGRP is released during migraine pain, the NO-stimulated CGRP release may be relevant for the development of vascular headaches that are accompanied by meningeal hyperaemia." [Abstract]

Strecker T, Dux M, Messlinger K.
Nitric oxide releases calcitonin-gene-related peptide from rat dura mater encephali promoting increases in meningeal blood flow.
J Vasc Res. 2002 Nov-Dec;39(6):489-96.
"Nitric oxide (NO) and calcitonin-gene-related peptide (CGRP) are implicated in the pathophysiology of vascular headaches. We studied the interaction of these two vasodilatory mediators in an animal model and suggest that NO may increase meningeal blood flow not only by its direct vasodilatory action but also by stimulating CGRP release. First, CGRP release from the rat cranial dura mater was measured in vitro using an enzyme immunoassay. Hemisected skulls with adhering dura mater were filled with synthetic interstitial fluid and stimulated with the NO donor diethylamine-NONOate (10(-5)-10(-3) M) or with NO gas (1,000 ppm), which caused concentration-dependent increases in CGRP release up to 166.8%. Second, meningeal blood flow was recorded in vivo in the exposed dura mater using laser Doppler flowmetry. Topical application of the NO donors NONOate, S-nitroso-N-acetylpenicillamine and N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino)-ethenamine (10(-5)-10(-3) M) caused concentration-dependent increases in blood flow. These increases were significantly reduced by local preliminary application of the CGRP receptor antagonist CGRP(8-37) (10(-4) M). We conclude that NO stimulates the release of CGRP from dural afferents. The blood-flow-increasing effect of NO seems to be partly mediated by CGRP. The interaction of NO and CGRP may be relevant for the development of vascular headaches." [Abstract]

Strecker T, Dux M, Messlinger K.
Increase in meningeal blood flow by nitric oxide--interaction with calcitonin gene-related peptide receptor and prostaglandin synthesis inhibition.
Cephalalgia. 2002 Apr;22(3):233-41.
"This study addresses possible interactions of the vasodilators nitric oxide (NO), calcitonin gene-related peptide (CGRP) and prostaglandins, which may be implicated in the generation of vascular headaches. Local application of the NO donator diethylamine-NONOate (NONOate) to the exposed dura mater encephali of the rat caused dose-dependent increases in meningeal blood flow recorded by laser Doppler flowmetry. Pre-application of the CGRP receptor antagonist CGRP8-37 significantly attenuated the evoked blood flow increases, while the cyclooxygenase inhibitors acetylsalicylic acid and metamizol were only marginally effective. Stimulation of rat dura mater with NONOate in vitro caused increases in CGRP release. NADPH-diaphorase activity indicating NO production was restricted to the endothelium of dural arterial vessels. We conclude that increases in meningeal blood flow caused by NO depend partly on the release and vasodilatory action of CGRP from dural afferents, while prostaglandins are not significantly involved." [Abstract]

Gallai V, Alberti A, Gallai B, Coppola F, Floridi A, Sarchielli P.
Glutamate and nitric oxide pathway in chronic daily headache: evidence from cerebrospinal fluid.
Cephalalgia. 2003 Apr;23(3):166-74.
"A central sensitization has been advocated to explain chronic daily headache (CDH) due to sustained peripheral sensitization of allogenic structures responsible for sustained trigeminovascular system activation. Several mechanisms have been suggested to underlie central sensitization, but have been poorly investigated in CDH. They involve N-methyl-D-aspartate (NMDA) receptor activation and nitric oxide (NO) production and supersensitivity and increased and maintained production of sensory neuropeptides. The present study supports the above pathogenic mechanisms demonstrating a significant increase in glutamate and nitrite levels in the CSF of CDH patients, without a significant difference between patients without and those with analgesic overuse headache (P < 0.0001 and P < 0.002). The increase in CSF nitrites was accompanied by a significant rise in the CSF values of cyclic guanosine monophosphate (cGMP) in patients in comparison with controls (P < 0.0001). A statistically significant correlation emerged between visual analogic scale (VAS) values and glutamate, nitrites and cGMP. Although substance P (SP) and calcitonin gene-related peptide (CGRP), and to a lesser extent neurokinin A, were significantly increased in CSF compared with control subjects, their values did not correlate with glutamate, nitrites and cGMP levels in CSF in the patient group. The present study confirms the involvement of glutamate-NO-cGMP-mediated events underlying chronic head pain that could be the target of a new therapeutic approach which should be investigated." [Abstract]

Eltorp CT, Jansen-Olesen I, Hansen AJ.
Release of calcitonin gene-related peptide (CGRP) from guinea pig dura mater in vitro is inhibited by sumatriptan but unaffected by nitric oxide.
Cephalalgia. 2000 Nov;20(9):838-44.
"Migraine attacks can be provoked by administration of nitroglycerin, suggesting a role for nitric oxide (NO). The fact that release of the neuropeptide CGRP from trigeminal sensory nerves occurs during the pain phase of migraine and that NO can augment transmitter release prompted us to study CGRP release from the in situ dura mater in guinea pig skulls. Release of CGRP by capsaicin or by high potassium concentration was concentration-dependent and counteracted in calcium-free medium. The anti-migraine compound, sumatriptan, inhibited CGRP release via the 5-HT1-receptor. The NO donors, nitroglycerin, sodium nitroprusside and S-nitroso-N-acetylpenicillamine did not influence CGRP release, alone or together with the stimulants. We concluded that the skull preparation is well suited for scrutinizing CGRP release from dura mater. The fact that sumatriptan inhibits CGRP release as in migraine patients suggests a use for the present preparation in headache research." [Abstract]

Ashina M, Bendtsen L, Jensen R, Schifter S, Olesen J.
Calcitonin gene-related peptide levels during nitric oxide-induced headache in patients with chronic tension-type headache.
Eur J Neurol. 2001 Mar;8(2):173-8.
"It has been proposed that nitric oxide (NO) induced headache in primary headaches may be associated with release of calcitonin gene-related peptide (CGRP). In the present study we aimed to investigate plasma levels of CGRP during headache induced by the NO donor glyceryl trinitrate (GTN) in 16 patients with chronic tension-type headache and 16 healthy controls. The subjects were randomly allocated to receive 0.5 microg/kg/min GTN or placebo over 20 min on two headache-free days. Blood samples were collected at baseline, 10, 20 and 60 min after start of infusion. Both patients and controls developed significantly stronger immediate headache on the GTN day than on the placebo day and the headache was significantly more pronounced in patients than in controls. There was no difference between the area under the CGRP curve (AUCCGRP) on GTN vs. placebo day in either patients (P=0.65) or controls (P=0.48). The AUCCGRP recorded on the GTN day did not differ between patients and controls (P=0.36). Both in patients and controls, CGRP levels changed significantly over time, on both the GTN and placebo days (P < 0.05). The present study indicates that NO-induced immediate headache is not associated with release of CGRP." [Abstract]

Messlinger K, Suzuki A, Pawlak M, Zehnter A, Schmidt RF.
Involvement of nitric oxide in the modulation of dural arterial blood flow in the rat.
Br J Pharmacol. 2000 Apr;129(7):1397-404.
"1. Nitric oxide (NO) has been proposed to be a key molecule in the pathogenesis of migraine pain and other headaches that are linked to vascular disorders. Several lines of evidence indicate that the meningeal vascularization is crucially involved in the generation of these headaches. In an experimental model in the rat a dominating role of calcitonin gene-related peptide (CGRP) in causing neurogenic vasodilatation and increased blood flow has been shown. The aim of the present study was to clarify the role of NO in this model with regard to the meningeal blood flow. 2. The blood flow in and around the medial meningeal artery (dural arterial flow) was recorded in the exposed parietal dura mater encephali of barbiturate anaesthetized rats using laser Doppler flowmetry. Local electrical stimulation of the dura mater (pulses of 0.5 ms delivered at 7.5 - 17.5 V and 5 or 10 Hz for 30 s) caused temporary increases in dural arterial flow for about 1 min that reached peaks of 1.6 - 2.6 times the basal flow. The effects of NO synthase (NOS) inhibitors on the basal flow and the electrically evoked increases in flow were examined. 3. Systemic (i. v.) administration of N(omega)-nitro-L-arginine methyl ester (L-NAME) at cumulative doses of 10 and 50 mg kg(-1) lowered the basal flow to 87 and 72%, respectively, of the control and reduced the evoked increases in blood flow to 82 and 44% on an average. Both these effects could partly be reversed by 300 mg kg(-1) L-arginine. The systemic arterial pressure was increased by L-NAME at both doses. Injection of the stereoisomer D-NAME at same doses did not change basal flow and evoked increases in flow. 4. 4. Topical application of L-NAME (10(-4) - 10(-2) M) was effective only at the highest concentration, which caused lowering of the basal blood flow to 78% of the control; the evoked increases in flow were not changed. Topical application of 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT), a specific inhibitor of the inducible NOS, at concentrations of 10(-4) - 10(-2) M lowered the basal flow to 89, 87.5 and 85%, respectively, but did not significantly change the evoked flow increases. Same concentrations of 7-nitroindazole monosodium salt (7-NINA), a specific inhibitor of the neuronal NOS, had no significant effects on basal flow and evoked increases in flow. 5. It is concluded that NO is involved in the maintenance of the basal level of dural arterial blood flow as well as in the electrically evoked flow increases, which have been shown to be mainly mediated by CGRP released from dural afferent fibres. The most important source of NO is probably the endothelium of dural arterial vessels. The synergistic effect of NO and CGRP on the stimulated blood flow may be in part due to a NO mediated facilitation of the CGRP release." [Abstract]

Akerman S, Williamson DJ, Kaube H, Goadsby PJ.
Nitric oxide synthase inhibitors can antagonize neurogenic and calcitonin gene-related peptide induced dilation of dural meningeal vessels.
Br J Pharmacol. 2002 Sep;137(1):62-8.
"1. The detailed pathophysiology of migraine is beginning to be understood and is likely to involve activation of trigeminovascular afferents. 2. Clinically effective anti-migraine compounds are believed to have actions that include peripheral inhibition of calcitonin gene-related peptide (CGRP) release from trigeminal neurones, or preventing dural vessel dilation, or both. CGRP antagonists can block both neurogenic and CGRP-induced dural vessel dilation. 3. Nitric oxide (NO) can induce headache in migraine patients and often triggers a delayed migraine. The initial headache is thought to be caused via a direct action of the NO-cGMP pathway that causes vasodilation by vascular smooth muscle relaxation, while the delayed headache is likely to be a result of triggering trigeminovascular activation. Nitric oxide synthase (NOS) inhibitors are effective in the treatment of acute migraine. 4. The present studies used intravital microscopy to examine the effects of specific NOS inhibitors on neurogenic dural vasodilation (NDV) and CGRP-induced dilation. 5. The non-specific and neuronal NOS (nNOS) inhibitors were able to partially inhibit NDV, while the non-specific and endothelial NOS (eNOS) inhibitors were able to partially inhibit the CGRP induced dilation. 6. There was no effect of the inducible NOS (iNOS) inhibitor. 7. The data suggest that the delayed headache response triggered by NO donors in humans may be due, in part, to increased nNOS activity in the trigeminal system that causes CGRP release and dural vessel dilation. 8. Further, eNOS activity in the endothelium causes NO production and smooth muscle relaxation by direct activation of the NO-cGMP pathway, and may be involved in the initial headache response." [Abstract]

Ashina M, Lassen LH, Bendtsen L, Jensen R, Olesen J.
Effect of inhibition of nitric oxide synthase on chronic tension-type headache: a randomised crossover trial.
Lancet. 1999 Jan 23;353(9149):287-9.
"BACKGROUND: Studies in animals have shown that nitric oxide plays an important part in central sensitisation and that inhibitors of nitric oxide synthase (NOS) decrease sensitisation in models of persistent pain. The efficacy of inhibitors of NOS has not been tested in patients with tension-type chronic headache. We aimed to show whether N(G)-monomethyl-L-arginine hydrochloride (L-NMMA), an inhibitor of NOS, is effective in relieving pain in such patients. METHODS: We undertook a randomised double-blind, crossover trial of 16 patients with chronic-tension-type headache. Patients were assigned intravenous infusion of 6 mg/kg L-NMMA or placebo on 2 days separated by at least 1 week in a randomised order. Headache intensity was measured on a 100 mm visual analogue scale, and on a verbal rating scale at baseline and at 30 min, 60 min, and 120 min after start of treatment. The primary endpoint was reduction of pain intensity on the visual analogue scale by the active treatment compared with placebo. FINDINGS: L-NMMA reduced pain intensity on the visual analogue scale significantly more than placebo: 120 min after start of treatment, the mean pain score was decreased from 49 to 33 with L-NMMA and from 44 to 40 with placebo (p=0.01). Pain intensity on the verbal rating scale was also significantly lower for treatment with L-NMMA than for treatment with placebo (p=0.02). INTERPRETATION: Inhibition of NOS had an analgesic effect in chronic tension-type headache. Further tests are required before clinical application." [Abstract]

Lassen LH, Ashina M, Christiansen I, Ulrich V, Grover R, Donaldson J, Olesen J.
Nitric oxide synthase inhibition: a new principle in the treatment of migraine attacks.
Cephalalgia. 1998 Jan;18(1):27-32.
"Glyceryl trinitrate, an exogenous nitric oxide (NO) donor, and histamine, which causes NO formation in vascular endothelium, have been shown to trigger migraine attacks. However, it remains uncertain whether NO is involved in the subsequent phase of migraine attacks. To answer this question we studied the effect of L-NGmethylarginine hydrochloride (546C88), a NO-synthase inhibitor, on spontaneous migraine attacks. In a double-blind study design, 18 patients with migraine without aura randomly received 546C88 (6 mg/kg) or placebo (5% dextrose) i.v. given over 15 min for a single migraine attack (546C88:placebo, 15:3). Furthermore, 11 placebo-treated patients from previous double-blind trials with almost identical design were added to the placebo group in the statistical evaluation. Two hours after the infusion, 10 of 15 L-NGmethylarginine hydrochloride-treated patients experienced headache relief compared to 2 of 14 placebo-treated patients (p = 0.01). Symptoms such as phono- and photophobia were also significantly improved. A similar trend for nausea was not significant. We conclude that NO may be involved in the pain mechanisms throughout the course of spontaneous migraine attacks." [Abstract]

van der Kuy PH, Merkus FW, Lohman JJ, ter Berg JW, Hooymans PM.
Hydroxocobalamin, a nitric oxide scavenger, in the prophylaxis of migraine: an open, pilot study.
Cephalalgia. 2002 Sep;22(7):513-9.
"Drugs which directly counteract nitric oxide (NO), such as endothelial receptor blockers, NO-synthase inhibitors, and NO-scavengers, may be effective in the acute treatment of migraine, but are also likely to be effective in migraine prophylaxis. In the underlying pilot study the prophylactic effect of the NO scavenger hydroxocobalamin after intranasal administration in migraine was evaluated. Twenty patients, with a history of migraine of > 1 year and with two to eight migraine attacks per month, were included in an open trial. A baseline period was followed by an active treatment period of 3 months with 1 mg intranasal hydroxocobalamin daily. Patients were instructed to complete a diary in which details of each attack were described. A reduction in migraine attack frequency of >/ or = 50% was seen in 10 of 19 patients, which corresponds to 53% of the patients (responders). A reduction of > or = 30% was noted in 63% of the patients. The mean attack frequency in the total study population showed a reduction from 4.7 +/- 1.7 attacks per month to 2.7 +/- 1.6 (P < 0.001). For the responders the migraine attack frequency was reduced from 5.2 +/- 1.9 (baseline) to 1.9 +/- 1.3 attacks per month (P < 0.005), while for those who did not respond a non-significant reduction was found: 4.1 +/- 1.4 to 3.7 +/- 1.5 (P > 0.1). A reduction was also observed for the total duration of the migraine attacks per month, the total number of migraine days per month and the number of medication doses for acute treatment used per month. This is the first prospective, open study indicating that intranasal hydroxocobalamin may have a prophylactic effect in migraine. As a percentage of responders in prophylactic trials of > 35-40% is unlikely to be a placebo effect, a double-blind study is warranted." [Abstract]

Read SJ, Parsons AA.
Sumatriptan modifies cortical free radical release during cortical spreading depression. A novel antimigraine action for sumatriptan?
Brain Res. 2000 Jul 7;870(1-2):44-53.
"Increases in concentration of brain NO are proposed to initiate and mediate migraine headache. Triggered by focal depolarisation, spreading depression (SD) represents a suitable mechanism for eliciting widespread release of nitric oxide. The current study examines the effect of sumatriptan, a 5-HT(1B/1D) agonist and effective antimigraine therapy, on free radical release (nitric oxide and superoxide) in SD in the simple and complex cortices of the rat and cat. Following initiation of SD, sumatriptan pretreatment (300 microg kg(-1) i.v., 15 min prior to SD) modulated all phases of nitric oxide release associated with each SD in both cats and rats. As a result, superoxide levels were observed to significantly (ANOVA, post hoc LSD) increase versus vehicle treated animals (saline 1 ml kg(-1) i.v. 15 min prior to SD) during specific phases of each SD depolarisation. Averaged over all SD depolarisations, mean peak SD nitric oxide levels per depolarisation were 0.73+/-0.23 microM (n=29) in cats, and 0.42+/-0.09 microM (n=34) in rats. Sumatriptan significantly (Students t-test, P<0.05, two tailed hypothesis, P<0.05) modulated this increase in cortical nitric oxide concentrations to 0.32+/-0.06 microM (n=25) and 0. 22+/-0.07 microM (n=37) in cats and rats. Sumatriptan appears to decrease the amplitude of nitric oxide release but enhances extracellular superoxide concentrations in both lissencephalic and gyrencephalic cortices during SD." [Abstract]

Ikeda Y, Jimbo H, Shimazu M, Satoh K.
Sumatriptan scavenges superoxide, hydroxyl, and nitric oxide radicals: in vitro electron spin resonance study.
Headache. 2002 Oct;42(9):888-92.
"BACKGROUND: The molecular mechanisms of migraine have not yet been clarified. Oxygen free radicals have been implicated in the genesis of many pathological processes, including migraine. Sumatriptan succinate is known to be a very effective drug for acute relief of migraine attack. OBJECTIVE: To investigate the direct scavenging activities of sumatriptan for superoxide, hydroxyl, and nitric oxide (NO) radicals using electron spin resonance (ESR) spectroscopy. METHODS: Measurement of superoxide and hydroxyl radical scavenging activities was performed by ESR using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap. NO was generated from 1-hydroxy-2-oxo-3-(N-3-methyl-3-aminopropyl)-3-methyl-1-triazene and analyzed by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl produced from the reaction between 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and NO. RESULTS: The ESR study demonstrated that sumatriptan scavenged superoxide, hydroxyl, and NO in a dose-dependent manner. CONCLUSIONS: Sumatriptan has direct scavenging activity on free radicals and NO. Acute migraine drugs with antioxidant properties may provide heretofore unheralded benefits via this mechanism." [Abstract]

Read SJ, Manning P, McNeil CJ, Hunter AJ, Parsons AA.
Effects of sumatriptan on nitric oxide and superoxide balance during glyceryl trinitrate infusion in the rat. Implications for antimigraine mechanisms.
Brain Res. 1999 Nov 13;847(1):1-8.
"Infusion of glyceryl trinitrate (GTN) into patients with migraine precipitates the onset of a migraine attack several hours after completion of the infusion. Using an infusion of GTN into anaesthetised rats, this study investigates the relationship of regional cerebral blood flux rCBF(ldf), cortical nitric oxide (NO) and cortical superoxide concentrations and the effect of sumatriptan on each variable. In saline treated animals, a 30 min infusion of GTN (2 microgram kg(-1) min(-1), i.v.) was found to markedly increase cortical rCBF(ldf) (133+/-3% of baseline) and NO concentrations (141+/-13% of baseline). Superoxide levels exhibited an inverse relationship to NO levels, decreasing below basal to 48+/-14% of baseline. It is hypothesised that high NO levels during GTN infusion may decrease the detectable superoxide due to "leeching" of the superoxide into low level peroxynitrite formation. In the presence of sumatriptan, a decrease below baseline in cortical rCBF(ldf) (82+/-5% of baseline) and NO concentration (64+/-13% of baseline) was observed throughout GTN infusion, although superoxide levels significantly increased above baseline by 105+/-14 nM (p<0.05, ANOVA post hoc LSD test). The mechanism for this action of sumatriptan is unknown but may include; modulation of cell redox state, NO scavenging or direct manipulation of superoxide release." [Abstract]

Iversen HK, Olesen J.
Headache induced by a nitric oxide donor (nitroglycerin) responds to sumatriptan. A human model for development of migraine drugs.
Cephalalgia. 1996 Oct;16(6):412-8.
"Experimental "vascular" headache in humans may be used in characterizing new migraine drugs. The effects of sumatriptan on nitroglycerin-(NTG)-induced headache and arterial responses were therefore studied. Following a double-blind randomized crossover design, 10 healthy volunteers received sumatriptan 6 mg s.c. or placebo succeeded by 20 min NTG (0.12 microgram/kg/min) infusion. Headache was rated on a 10 points scale. Temporal and radial artery diameters and velocity in the middle cerebral artery (MCA) were measured with ultrasound. Sumatriptan reduced the NTG-induced headache, median score 1.5 versus 4 after placebo (p < 0.01) and decreased temporal and radial artery diameters 75 +/- 3 and 86 +/- 3% of baseline respectively (p < 0.05). Blood velocity in the MCA was unaffected. The NTG model may prove to be a valuable tool in the development of future migraine drugs. The results suggest that NTG headache in non-migraineurs may share mechanisms with migraine headache." [Abstract]

Akerman S, Williamson DJ, Kaube H, Goadsby PJ.
The effect of anti-migraine compounds on nitric oxide-induced dilation of dural meningeal vessels.
Eur J Pharmacol. 2002 Oct 4;452(2):223-8.
"Migraine is characteristically accompanied by a throbbing quality of head pain thought to involve trigeminovascular afferents. Administration of nitric oxide (NO) donors provides the most reliable model of migraine induction in humans. The present studies used intravital microscopy to monitor the effect of local meningeal nerve stimulation and NO on dural blood vessels and any modulation of that effect by anti-migraine compounds. NO caused an immediate and reproducible dilation of meningeal blood vessels that was partially blocked by sumatriptan and indomethacin, while flunarizine and histamine H(1) and H(2) receptor antagonists were unable to block the dilation. Indomethacin also inhibited the neurogenic dilation while flunarizine did not. The present studies demonstrate that NO is unlikely to interact with histamine to produce its dilatory response. Sumatriptan and indomethacin inhibit the NO response by inhibiting trigeminal activation and calcitonin gene-related peptide (CGRP) release. Flunarizine does not modify either the neurogenic vasodilator response or the NO meningeal dilator response at least acutely." [Abstract]

Ayajiki K, Okamura T, Toda N.
Flunarizine, an anti-migraine agent, impairs nitroxidergic nerve function in cerebral arteries.
Eur J Pharmacol. 1997 Jun 18;329(1):49-53.
"Flunarizine is an anti-migraine agent that blocks the Ca2+ entry across cell membrane. In order to obtain a clue of mechanisms underlying the migraine headache, modifications by flunarizine of the response to nitric oxide (NO), a cerebral vasodilator and algogenic agent, derived from perivascular nerves were evaluated. Relaxations due to nerve stimulation by electrical pulses (5 Hz) and nicotine (10(-4) M) in canine cerebral arterial strips were attenuated by treatment with flunarizine dose-dependently, whereas the responses to exogenous NO (10(-7)-10(-6) M) and nitroprusside (10(-8)-10(-6) M) were unaffected. The inhibition by the Ca2+ entry blocker of the response to electrical nerve stimulation and nicotine was obtained in a concentration (10(-6) M) that did not significantly relax the arterial strips. NO derived from perivascular nerve may be one of the factors involved in the genesis of migraine attack, which is expected to be relieved by a reduction of neural NO synthase activity associated with a decreased Ca2+ influx by flunarizine during nerve activation." [Abstract]

Nattero G, Mengozzi G, Inconis T, Paradisi L.
Nitric oxide, endothelin-1, and transcranial Doppler in migraine. Findings in interictal conditions and during migraine attack.
Headache. 1996 May;36(5):307-11.
"The role of vascular phenomena taking place during an attack of migraine are poorly understood. The aim of this study was to measure systemic levels of nitric oxide and endothelin-1, two of the most potent vasoactive mediators known, and to assess vasomotor responses through transcranial Doppler ultrasound monitoring in patients suffering from migraine without aura, both during the headache event and in headache-free periods as well as after pharmacologically induced pain relief. Seven patients (mean age 31.3 years, range 24 to 49 years), five women and two men, were enrolled in the pilot study. Transcranial Doppler recordings were performed according to conventional procedure. Endothelin-1 concentrations were measured by means of radioimmunoassay, whereas nitric oxide levels were estimated using electron paramagnetic resonance spectroscopy. Ultrasound evaluation did not show significant changes during migraine attacks compared to the interictal condition. Nitric oxide levels showed only slight differences between basal and attack conditions (0.85 +/- 0.46 versus 1.56 +/- 0.88, expressed as arbitrary units), and were raised after pharmacological intervention (2.91 +/- 1.93, P < 0.05). Plasma endothelin-1 concentrations decreased during migraine attacks with respect to interictal conditions (3.99 +/- 1.21 pg/mL versus 4.23 +/- 1.19), and returned to basal values (4.44 +/- 1.08 pg/mL) after relief of pain. Coupling the measurements of systemic levels of nitric oxide and endothelin-1 with transcranial Doppler velocity results will provide useful information on the hemodynamic changes of cerebral blood flow regulation in migraineurs, thereby adding new insights into the mechanisms of the migraine attack." [Abstract]

Pardutz A, Krizbai I, Multon S, Vecsei L, Schoenen J.
Systemic nitroglycerin increases nNOS levels in rat trigeminal nucleus caudalis.
Neuroreport. 2000 Sep 28;11(14):3071-5.
"Systemic administration of nitroglycerin, a nitric oxide donor, triggers in migraineurs a delayed attack of unknown mechanisms. Subcutaneous nitroglycerin (10 mg/kg) produced a significant increase of nitric oxide synthase (NOS)- and c-fos-immunoreactive neurons in the cervical part of trigeminal nucleus caudalis in rats after 4 h. This effect was not observed in the thoracic dorsal horn. Similar increase of NOS and c-fos was obtained in the brain stem after a somatic nociceptive stimulus, i.e. on the side of the formalin injection in the lip. Nitric oxide is thus able to increase NOS availability in second order nociceptive trigeminal neurons, which may be relevant for central sensitization and the understanding of its effect in migraine." [Abstract]

Knyihar-Csillik E, Vecsei L.
Effect of a nitric oxide donor on nitroxergic nerve fibers in the rat dura mater.
Neurosci Lett. 1999 Jan 29;260(2):97-100.
"Nitroglycerine, given subcutaneously to rats (10 mg/kg body weight) induces increased beading of nitric oxide synthase immunoreactive (NOS-IR) nerve fibers in the supratentorial cerebral dura mater, and an apparent increase in the number of NOS-IR nerve fibers in the dural areas supplied by the anterior and middle meningeal arteries, and the sinus sagittalis superior. Structural alterations of nitroxergic axons innervating blood vessels of the dura mater support the idea that nitric oxide is involved in the induction of headache also by a primary peripheral action, a well-known side effect of coronary dilator agents." [Abstract]

Hoskin KL, Bulmer DC, Goadsby PJ.
Fos expression in the trigeminocervical complex of the cat after stimulation of the superior sagittal sinus is reduced by L-NAME.
Neurosci Lett. 1999 May 14;266(3):173-6.
"Primary neurovascular headaches, such as migraine and cluster headache probably involve activation of trigeminovascular pain structures projecting to the trigeminocervical complex of neurons in the caudal brain stem and upper cervical spinal cord. It has recently been demonstrated that blockade of the synthesis of nitric oxide (NO) by an NO synthesis inhibitor can abort acute migraine attacks and thus it is of interest to determine whether there is an influence of NO generation on trigeminocervical neurons. Cats were anaesthetised with alpha-chloralose (60 mg/kg, i.t.). supplemental 20 mg/kg, intravenously (i.v.)) and halothane for surgery (0.5-3% by inhalation). A circular midline craniotomy was performed to isolate the superior sagittal sinus (SSS) for electrical stimulation (0.3 Hz, 150 V, 250 micros duration for 2 h). Two groups were compared, one stimulated after administration of vehicle and the other stimulated after administration of N(G)-nitro-L-arginine methylester (L-NAME: 100 mg/kg, i.v.). After stimulation of the SSS Fos immunoreactivity was observed in lamina I/IIo of the trigeminal nucleus caudalis and dorsal horns of C1 and C2 to a median total of 136 cells (range 122-146). After L-NAME treatment Fos expression was significantly reduced to 40 cells (24-54; P < 0.02). In conclusion, inhibition of NO synthesis L-NAME markedly reduces Fos expression in the trigeminocervical complex of the cat. These data taken together with the clinical observations of the effect of NO synthesis blockade in migraine suggest a role for NO generation in mediating nociceptive transmission in acute migraine." [Abstract]

De Col R, Koulchitsky SV, Messlinger KB.
Nitric oxide synthase inhibition lowers activity of neurons with meningeal input in the rat spinal trigeminal nucleus.
Neuroreport. 2003 Feb 10;14(2):229-32.
"Nitric oxide is thought to control transmitter release and neuronal activity in the spinal dorsal horn and the spinal trigeminal nucleus, where nociceptive information from extra- and intracranial tissues is processed. Extracellular impulse activity was recorded from neurons in the rat spinal trigeminal nucleus with afferent input from the cranial dura mater. In contrast to the inactive isomer D-NAME, infusion of the nitric oxide synthase inhibitor L-NAME (20 mg/kg) significantly reduced neuronal activity and increased systemic blood pressure. It is concluded that nitric oxide production contributes to the ongoing activity of sensitized neurons in the spinal trigeminal nucleus. The results suggest that nitric oxide may be involved in the generation and maintenance of primary headaches such as migraine." [Abstract]

Jones MG, Lever I, Bingham S, Read S, McMahon SB, Parsons A.
Nitric oxide potentiates response of trigeminal neurones to dural or facial stimulation in the rat.
Cephalalgia. 2001 Jul;21(6):643-55.
"Infusing glyceryl trinitrate as a donor molecule, we have used electrophysiological and c-fos immunostaining techniques to study the effects of nitric oxide on neurones in the nucleus trigeminalis caudalis. Following infusion of glyceryl trinitrate, responses of neurones to electrical stimulation of periorbital cutaneous afferents were potentiated and threshold for activation of neurones by stimulation of dural afferents was reduced. Expression of c-fos was unchanged by glyceryl trinitrate compared to saline controls. Intradermal injection of capsaicin in the periorbital area increased c-fos expression in nucleus trigeminalis caudalis; this was significantly potentiated by glyceryl trinitrate. These results suggest that, in the anaesthetized rat, glyceryl trinitrate alone may not acutely activate the trigeminovascular system to a significant degree at doses that cause headache and later trigger migraine headache in migraineurs. Nevertheless, it is susceptible to exogenous nitric oxide in that activation of trigeminal neurones through cutaneous or dural pathways is potentiated. This may in some measure underlie the pathogenesis of migraine headache." [Abstract]

Behrends S, Knyihar-Csillik E, Kempfert J, Scholz H, Csillik B, Vecsei L.
Glyceryl trinitrate treatment up-regulates soluble guanylyl cyclase in rat dura mater.
Neuroreport. 2001 Dec 21;12(18):3993-6.
"Nitric oxide (NO) is a key molecule in vascular headaches and the dura mater has been implicated as a tissue where vascular headache develops. Here we demonstrate expression, enzyme activity and cellular distribution of the intracellular receptor for NO, soluble guanylyl cyclase (sGC), in rat dura mater. Subcutaneous treatment of rats with the NO-donor glyceryl trinitrate (GTN) induced an increase of sGC expression and activity in dural blood vessels after 20-30 min. It has previously been shown that GTN induces headache in normal subjects after 20-30 min. Our findings suggest that an up-regulation of the NO target enzyme contributes to the pathogenesis of GTN-induced headache explaining the subacute rather than acute onset of symptoms." [Abstract]

Nemade RV, Lewis AI, Zuccarello M, Keller JT.
Immunohistochemical localization of endothelial nitric oxide synthase in vessels of the dura mater of the Sprague-Dawley rat.
Neurosci Lett. 1995 Sep 1;197(1):78-80.
"Nitric oxide (NO) and the dura mater are implicated in the pathogenesis of vascular headache. Many studies have demonstrated the participation of NO in headache; however, few studies have identified NO in the dura mater. In this study, nine Sprague-Dawley rats were examined with immunohistochemistry using two different endothelial nitric oxide synthase (eNOS) monoclonal antibodies, H32 and ECNOS. eNOS was successfully localized to the endothelium of the middle meningeal artery. To the best of our knowledge, this is the first study to report NOS immunopositive endothelial cells in the blood vessels of the rat dura mater. The authors propose that NO plays an active role in dural vasodilation, contributing to the pathogenesis of vascular headache; in the future, NO inhibitors could serve as pharmacological agents to treat vascular headache." [Abstract]

Valenzuela RF, Donoso MV, Mellado PA, Huidobro-Toro JP.
Migraine, but not subarachnoid hemorrhage, is associated with differentially increased NPY-like immunoreactivity in the CSF.
J Neurol Sci. 2000 Feb 15;173(2):140-6.
"To test whether migraine and subarachnoid hemorrhage (SAH) are associated with increased sympathetic tone, we compared the neuropeptide Y-like (NPY-LI) and chromogranin A-like immunoreactivities (LI) of cerebrospinal fluid (CSF) from migraneurs and SAH patients with those from control subjects. Increased sympathetic tone was expected to produce higher co-release of these co-stored peptides and concordant changes in their CSF levels. In addition, we investigated a possible disturbed nitric oxide homeostasis by measuring CSF nitrites (NO). More than 70% of CSF NPY-LI corresponded to the chromatographic peak (HPLC) for the intact molecule in all three groups. Migraneurs had 64% higher CSF NPY-LI, but no significant difference in CSF chromogranin A-LI, as compared to controls. In contrast, SAH patients had 74% less CSF chromogranin A-LI and a trend to lower NPY-LI, as compared to controls. No differences in CSF NO were detected among groups. These results argue against an increased sympathetic tone in patients with either migraine or SAH, and suggest that the higher CSF NPY-LI of migraneurs probably originates from central neurons. Furthermore, our findings in SAH patients argue in favor of a decreased sympathetic tone; this could be a homeostatic response to counterbalance vasoconstriction mediated by other mechanisms." [Abstract]

Reuter U, Chiarugi A, Bolay H, Moskowitz MA.
Nuclear factor-kappaB as a molecular target for migraine therapy.
Ann Neurol. 2002 Apr;51(4):507-16.
"Nitric oxide (NO) generated from inducible NO synthase (iNOS) participates in immune and inflammatory responses in many tissues. The NO donor glyceryl trinitrate (GTN) provokes delayed migraine attacks when infused into migraineurs and also causes iNOS expression and delayed inflammation within rodent dura mater. Sodium nitroprusside, an NO donor as well, also increases iNOS expression. Because inflammation and iNOS are potential therapeutic targets, we examined transcriptional regulation of iNOS following GTN infusion and the consequences of its inhibition within dura mater. We show that intravenous GTN increases NO production within macrophages. L-N(6)-(1-iminoethyl)lysine, a selective iNOS inhibitor, attenuates the NO signal, emphasizing the importance of enzymatic activity to delayed NO production. iNOS expression is preceded by significant nuclear factor kappa B (NF-kappaB) activity, as reflected by a reduction in the inhibitory protein-kappa-Balpha (IkappaBalpha) and activation of NF-kappaB after GTN infusion. IkappaBalpha degradation, NF-kappaB activation, and iNOS expression were attenuated by parthenolide (3mg/kg), the active constituent of feverfew, an anti-inflammatory drug used for migraine treatment. These findings suggest that GTN promotes NF-kappaB activity and inflammation with a time course consistent with migraine attacks in susceptible individuals. We conclude, based on results with this animal model, that blockade of NF-kappaB activity provides a novel transcriptional target for the development of anti-migraine drugs." [Abstract]

Lea RA, Curtain RP, Shepherd AG, Brimage PJ, Griffiths LR.
No evidence for involvement of the human inducible nitric oxide synthase (iNOS) gene in susceptibility to typical migraine.
Am J Med Genet. 2001 Jan 8;105(1):110-3. [Abstract]

Christiansen I, Iversen HK, Olesen J.
Induction of nitrate tolerance is not a useful treatment in cluster headache.
Cephalalgia. 2000 Jun;20(5):445-54. [Abstract]

Christiansen I, Iversen HK, Olesen J.
Headache characteristics during the development of tolerance to nitrates: pathophysiological implications.
Cephalalgia. 2000 Jun;20(5):437-44.
"Recent studies suggest that nitric oxide (NO) plays an important role in nitrate-induced headache and in spontaneous migraine attacks. Organic nitrates act as prodrugs for NO and headache is a predominant adverse effect of nitrates but often disappears during continuous treatment. Insight into tolerance to headache could lead to insight into vascular headache mechanisms in general. The specific aim of the present study was therefore to characterize the headache and accompanying symptoms during continuous nitrate administration until a state of tolerance to headache had developed. 5-isosorbide-mononitrate (5-ISMN) 30 mg three times daily was administered orally for 7 days in 11 healthy subjects in a double-blind, randomized placebo controlled cross-over design. Wash-out between periods was 14 days or more. Haemodynamic data from the present study were compared to the observed changes of headache over time. Headache during 5-ISMN was longer lasting and more severe compared to placebo (P<0.004). In 10 subjects the headache fulfilled the pain sub-criteria for migraine and in five subjects all diagnostic criteria for migraine without aura were fulfilled. Conversely, 20 min of intravenous infusion of glyceryl trinitrate caused a milder headache and no migraine. The present results therefore suggest that NO may elicit a migraine attack in many healthy subjects if a high enough dose is given for several hours. A close temporal association between the disappearance of headache and the attenuation of the 5-ISMN induced dilatation of the superficial temporal artery was observed. In contrast, tolerance in the middle cerebral artery already appeared after 24 h, which was earlier than the development of tolerance to headache. If vasodilatation is the cause of headache the results point to extracerebral arteries. However, cytotoxic and pain modulating central nervous system effects of NO, the time courses of which are unknown, may also play a role, involving both intra- and extracranial arteries." [Abstract]

Stepien A, Chalimoniuk M.
Level of nitric oxide-dependent cGMP in patients with migraine.
Cephalalgia. 1998 Nov;18(9):631-4.
"It is believed that nitric oxide (NO) plays a significant role in migraine attacks. This molecule is formed due to the conversion of L-arginine into L-citrulline. The target receptor for NO is ferrum in the heme group of cytoplasmic guanyl cyclase, the enzyme catalyzing cyclic guanosine monophosphate (cGMP) formation. To confirm this hypothesis, cGMP and nitrite level in the blood serum were measured in patients with migraine. The group under study included 37 subjects suffering from migraine with and without aura and 40 normal control subjects. The cGMP was measured during a migraine attack and 60 min following the administration of sumatriptan 6 mg subcutaneously. A statistically significant increase in cGMP level was observed in patients during a migraine attack compared to the controls. This level decreased after the administration of sumatriptan, but it was still higher than in the controls. No correlation was found between the increased cGMP level and pain intensification with clinical symptoms of migraine. The results suggest the participation of biochemical changes in migraine pathogenesis in the L-arginine-NO-cGMP pathway." [Abstract]

Gallai V, Floridi A, Mazzotta G, Codini M, Tognoloni M, Vulcano MR, Sartori M, Russo S, Alberti A, Michele F, Sarchielli P.
L-arginine/nitric oxide pathway activation in platelets of migraine patients with and without aura.
Acta Neurol Scand. 1996 Aug;94(2):151-60.
"Nitric oxide (NO) in platelets has been proposed as a promising tool for studying NO variations in migraine. In the present research the platelet response to collagen and the basal and collagen-induced production of NO and cGMP in platelet cytosol were assessed in migraine patients (25 with aura and 35 without aura) both interictally and ictally, and compared with the same parameters in 30 age-matched control subjects. A reduced responsiveness to collagen was found in migraine patients, particularly those with aura, and this was more marked during attacks (ANOVA interictal periods: p < 0.01, attacks: p < 0.02) The basal and collagen-stimulated production of NO and cGMP in the platelet cytosol was significantly higher in migraine patients with aura assessed in interictal periods than in control subjects, and this production was further increased during attacks (interictal period: NO ANOVA: p < 0.001, ictal period: p < 0.01; cGMP: interictal period p < 0.01, ictal period: p < 0.02). The increase in platelet NO and cGMP production was also evident, though to a lesser extent, in migraine patients without aura. The present research supports the hypothesis of an activation of the L-arginine/NO pathway in migraine patients, especially those with aura, and confirms the findings of a previous study of increased levels of L-arginine in platelets of migraine patients studied in headache free-periods, and decreased collagen aggregation in whole blood." [Abstract]