Nitric oxide in primary headaches

Subcutaneous histamine versus sodium valproate in migraine prophylaxis: a randomized, controlled, double-blind study

Histamine has a selective affinity for H3-receptors and it may specifically inhibit the neurogenic edema response involved in migraine pathophysiology. The objective of this study was to evaluate the therapeutic potential of subcutaneous administration of histamine in migraine prophylaxis, compared with oral administration of sodium valproate, in an open clinical trial. Ninety-two patients with migraine were selected under criteria established by the International Headache Society and enrolled in a 12-week double-blind controlled clinical trial to evaluate the efficacy of subcutaneous administration of histamine (1-10 ng twice a week; n = 46) compared with oral administration of sodium valproate (500 mg daily dose; n = 46). The variables studied were headache intensity, frequency, duration, analgesic intake and migraine disability assessment (MIDAS). Two-tailed Student's t- test was used to compare means and the Mann-Whitney U and anova tests were used. The data collected during the 4th, 8th and 12th weeks of treatment revealed that histamine caused a significantly greater reduction (P < 0.001) in intensity and duration of migraine attacks as well as in analgesic intake. No difference was detected in the frequency of attacks or in MIDAS. The present study provides evidence of the superior efficacy of histamine applied subcutaneously in migraine prophylaxis when compared with sodium valproate taken orally. Subcutaneously applied histamine may represent a novel and effective therapeutic alternative in resistant migraine patients.

Histamine and histamine intolerance

Histamine intolerance results from a disequilibrium of accumulated histamine and the capacity for histamine degradation. Histamine is a biogenic amine that occurs to various degrees in many foods. In healthy persons, dietary histamine can be rapidly detoxified by amine oxidases, whereas persons with low amine oxidase activity are at risk of histamine toxicity. Diamine oxidase (DAO) is the main enzyme for the metabolism of ingested histamine. It has been proposed that DAO, when functioning as a secretory protein, may be responsible for scavenging extracellular histamine after mediator release. Conversely, histamine N-methyltransferase, the other important enzyme inactivating histamine, is a cytosolic protein that can convert histamine only in the intracellular space of cells. An impaired histamine degradation based on reduced DAO activity and the resulting histamine excess may cause numerous symptoms mimicking an allergic reaction. The ingestion of histamine-rich food or of alcohol or drugs that release histamine or block DAO may provoke diarrhea, headache, rhinoconjunctival symptoms, asthma, hypotension, arrhythmia, urticaria, pruritus, flushing, and other conditions in patients with histamine intolerance. Symptoms can be reduced by a histamine-free diet or be eliminated by antihistamines. However, because of the multifaceted nature of the symptoms, the existence of histamine intolerance has been underestimated, and further studies based on double-blind, placebo-controlled provocations are needed. In patients in whom the abovementioned symptoms are triggered by the corresponding substances and who have a negative diagnosis of allergy or internal disorders, histamine intolerance should be considered as an underlying pathomechanism.

Potential role of female sex hormones in the pathophysiology of migraine

Clinical evidence indicates that female sex steroids may contribute to the high prevalence of migraine in women, as well as changes in the frequency or severity of migraine attacks that are in tandem with various reproductive milestones in women's life. While female sex steroids do not seem to be involved in the pathogenesis of migraine per se, they may modulate several mediators and/or receptor systems via both genomic and non-genomic mechanisms; these actions may be perpetuated at the central nervous system, as well as at the peripheral (neuro)vascular level. For example, female sex steroids have been shown to enhance: (i) neuronal excitability by elevating Ca(2+) and decreasing Mg(2+) concentrations, an action that may occur with other mechanisms triggering migraine; (ii) the synthesis and release of nitric oxide (NO) and neuropeptides, such as calcitonin gene-related peptide CGRP, a mechanism that reinforces vasodilatation and activates trigeminal sensory afferents with a subsequent stimulation of pain centres; and (iii) the function of receptors mediating vasodilatation, while the responses of receptors inducing vasoconstriction are attenuated. The serotonergic, adrenergic and gamma-aminobutyric acid (GABA)-ergic systems are also modulated by sex steroids, albeit to a varying degree and with potentially contrasting effects on migraine outcome. Taken together, female sex steroids seem to be involved in an array of components implicated in migraine pathogenesis. Future studies will further delineate the extent and the clinical relevance of each of these mechanisms, and will thus expand the knowledge on the femininity of migraine.

The headache-inducing effect of cilostazol in human volunteers

We have previously shown that nitric oxide (NO) and cyclic guanosine monophosphate (GMP) may cause headache and migraine. However, not all findings in previous studies can be explained by an activation of the NO-cGMP pathway. Calcitonin gene-related peptide (CGRP) causes headache and migraine in migraine patients, but CGRP receptor activation causes an increase in cyclic adenosine monophosphate (cAMP). In order to investigate the role of cAMP in vascular headache pathogenesis, we studied the effect of cilostazol, an inhibitor of cAMP degradation, in our human experimental headache model. Twelve healthy volunteers were included in a double-blind, randomized, crossover study. Placebo or cilostazol (200 mg p.o.) was administered on two separate study days. Headache was scored on a verbal rating scale (0-10) and mechanical pain thresholds were measured with von Frey hairs. The median peak headache score 0-16 h postdose was 0 (range 0-2) after placebo and 3.5 (range 0-7) after cilostazol (P = 0.003). The median headache curve peaked at 6-9 h postdose. The headaches induced were usually bilateral and pulsating. Nausea occurred in two volunteers, photo- and phonophobia were not seen. Two volunteers had a headache that fulfilled International Headache Society criteria for migraine without aura after cilostazol. No change in mechanical pain thresholds in the forehead was seen (P = 0.25). The headache after cilostazol was equal to or more severe than headache induced by glyceryl trinitrate in previous experiments. The present study thus indicates that increased levels of cAMP may play a role in headache and migraine pathogenesis.

Neurobiology of pain

The neurobiology of pain had a notable interest in research focused on the study of neuronal plasticity development, nociceptors, molecular identity, signaling mechanism, ionic channels involved in the generation, modulation and propagation of action potential in all type of excitable cells. All the findings open the possibility for developing new therapeutic treatment. Nociceptive/inflammatory pain and neuropathic pain represent two different kinds of persistent chronic pain. We have reviewed the different mechanism suggested for the maintenance of pain, like descending nociceptive mechanism and their changes after tissue damage, including suppression and facilitation of defence behavior during pain. The role of these changes in inducing NMDA and AMPA receptors gene expression, after prolonged inflammation is emphasized by several authors. Furthermore, a relation between a persistent pain and amygdale has been shown. Molecular biology is the new frontier in the study of neurobiology of pain. Since the entire genome has been studied, we will able to find new genes involved in specific condition such as pain, because an altered gene expression can regulate neuronal activity after inflammation or tissue damage.

NF-kappaB activity and iNOS expression in monocytes from internal jugular blood of migraine without aura patients during attacks

This study investigated nuclear factor-kappa B (NF-kappaB) activity by electrophoresis mobility gel shift assay and IkappaBalpha expression by Western blot analysis in monocytes obtained from serial samples of internal jugular venous blood taken from seven migraine patients without aura during attacks. Inducible nitric oxide synthase (iNOS) expression was also assessed by reverse transcription-polymerase chain reaction. An increase in NF-kappaB activity peaked 2 h after attack onset. This was accompanied by a transient reduction in IkappaBalpha expression. Up-regulation of iNOS was evident at 4 h, maintained at 6 h and reduced at the end of the attack. These findings substantiate the hypothesis of transitory delayed inflammation, as suggested by the animal model, and suggest the possibility of using therapeutic approaches to target NF-kappaB transcription in the treatment of migraine.

Distribution of NADPH diaphorase-exhibiting primary afferent neurons in the trigeminal ganglion and mesencephalic trigeminal nucleus of the rabbit

1. Nitric oxide (NO) is highly reactive gaseous molecule to which many physiological and pathological functions have been attributed in the central (CNS) and peripheral (PNS) nervous system. The present investigation was undertaken to map the distribution pattern of the enzyme responsible for the synthesis of NO, nitric oxide synthase (NOS), and especially its neuronal isoform (nNOS) in the population of primary afferent neurons of the trigeminal ganglion (TG) and mesencephalic trigeminal nucleus (MTN) of the rabbit. 2. In order to identify neuronal structures expressing nNOS we applied histochemistry to its specific histochemical marker nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd). 3. We found noticeable amount of NADPHd-exhibiting primary afferent neurons in TG of the rabbit under physiological conditions. The intensity of the histochemical reaction was highly variable reaching the maximum in the subpopulation of small-to-medium-sized neurons. The large-sized neurons were only weakly stained or actually did not posses any NADPHd-activity. In addition, NADPHd-positive nerve fibers were detected between clusters of the ganglionic cells and in the peripheral branches of the trigeminal nerve (TN). NADPHd-exhibiting MTN neurons were noticed in the whole rostrocaudal extent of the nucleus even though some differences were found concerning the ratio of NADPHd-positive versus NADPHd-negative cell bodies. Similarly, we observed striking diversity in the intensity of NADPHd histochemical reaction in the subpopulations of small-, medium-, and large-sized MTN neurons. 4. The predominant localization of NADPHd in the subpopulation of small-to-medium-sized TG neurons which are generally considered to be nociceptive suggests that NO probably takes part in the modulation of nociceptive inputs from the head and face. Furthermore, we tentatively assume that NADPHd-exhibiting MTN neurons probably participate in transmission and modulation of the proprioceptive impulses from muscle spindles of the masticatory muscles and mechanoreceptors of the periodontal ligaments and thus provide sensory feedback of the masticatory reflex arc.

Migraine: emerging treatment options for preventive and acute attack therapy

This review discusses emerging treatments of migraine in the context of what is now available. At present, patients are treated with a range of acute attack medicines or preventive treatments, with many having significant drawbacks. Important unmet needs are acute attack treatments that act by exclusively neural mechanisms with no vascular effects, and effective, well tolerated preventive medicines. Calcitonin gene-related peptide receptor antagonist, vanilloid receptor antagonists and nitric oxide synthase inhibitors are all in clinical trials for acute migraine. Tonaberset (a gap-junction blocker), an inducible nitric oxide synthase inhibitor and botulinum toxin A are in clinical trials for preventive therapy. Device-based approaches using neurostimulation of the occipital nerve are being studied, although the first study of patent foramen ovale closure for migraine prevention failed.

[Alimentary trigger factors that provoke migraine and tension-type headache]

Based on a review of the literature the authors discuss the role of nutrition in the precipitation of migraine and tension-type headache (TTH). The available information relies largely on the subjective assessment of the patients. Controlled trials suggest that alcohol and caffeine withdrawal are the most important nutritional precipitating factors of migraine and TTH. In addition, there is some evidence that missing meals is also an important factor. Dehydration seems to deserve more attention. A selective sensitivity to red wine has been shown in some patients, the importance of chocolate has been doubted seriously, and scientific evidence for cheese as a precipitating factor is lacking. Despite a series of experimental studies demonstrating that NO donors such as nitroglycerin and parenteral histamine cause headache the role of histamine, nitrates, and nitrites in food remains unclear. Similarly, other biogenic amines and aspartame have not been proven to precipitate headache. Sodium glutamate causes adverse reactions including headache probably at large doses ingested on an empty stomach. Therefore, patients should be advised that food plays a limited role as a precipitating factor of migraine and TTH. Subjective sensitivity to certain foods should be examined critically, and proven precipitating factors should be avoided. General dietary restrictions have not been proven to be useful.

Localization of soluble guanylyl cyclase in the superficial dorsal horn

Nitric oxide (NO) has been implicated in pain processing at the spinal level, but the mechanisms mediating its effects remain unclear. In the present work, we studied the organization of the major downstream effector of NO, soluble guanylyl cyclase (sGC), in the superficial dorsal horn of rat. Almost all neurokinin 1 (NK1) receptor-positive neurons in lamina I (a major source of ascending projections) were strongly immunopositive for sGC. Many local circuit neurons in laminae I-II also stained for sGC, but less intensely. Numerous fibers, presumably of unmyelinated primary afferent (C fiber) origin, stained for calcitonin gene-related peptide or isolectin B4, but none of these was immunopositive for sGC. These data, along with immunoelectron microscopy results, imply that unmyelinated primary afferent fibers terminating in the superficial dorsal horn lack sGC. Double labeling showed that neuronal nitric oxide synthase (nNOS) seldom colocalized with sGC, but nNOS-positive structures were frequently closely apposed to sGC-positive structures, suggesting that in the superficial dorsal horn NO acts mainly in a paracrine manner. Our data suggest that the NK1 receptor-positive projection neurons in lamina I are a major target of NO released in superficial dorsal horn. NO may also influence local circuit neurons, but it does not act on unmyelinated primary afferent terminals via sGC.

New targets in acute migraine treatment

Migraine is a common and highly disabling neurological problem, whose acute treatment was revolutionized by the triptans, serotonin 5-HT1B/1D receptor agonists. Some patients do not respond to triptans, while others are not suitable for them largely because of contraindications based on vascular disease. The exploration of nonvasoconstrictor treatments for acute migraine offers the prospect of dramatic improvements in patient care, as well as important insights into the mechanisms of migraine. Possibilities for such developments include, calcitonin gene-related peptide receptor antagonists, serotonin 5-HT1F and 5-HT1D receptor agonists, glutamate excitatory amino acid receptor antagonists, nitric oxide synthase inhibitors and adenosine A1 receptor agonists. Taken together, the future for migraine and affected patients is bright and promising.

Effects of Recombinant Human Thyrotropin on Heart Rate Variability and Blood Pressure in Patients on l-Thyroxine-Suppressive Therapy for Differentiated Thyroid Carcinoma

BACKGROUND

Recombinant human thyrotropin (rhTSH) is now currently used for the follow-up of patients with differentiated thyroid carcinoma (DTC) after total thyroid ablation. Side effects after rhTSH could involve the autonomic system and TSH receptors are possibly expressed in the heart and coronary arteries.

METHODS

Heart rate variability (HRV), studied by power spectral analysis of low (LF) and high frequency (HF) powers, blood pressure (BP) and their responses to orthostatism were investigated before and 3, 6, 9 days after the first of two administrations of rhTSH on alternate days in 11 patients on chronic l-thyroxine (l-T4) suppressive therapy for DTC and in 31 healthy controls.

RESULTS

A transient asymptomatic decrease in systolic and mean BP was observed during the rhTSH test, but rhTSH did not modify sympathovagal control of HRV and the lying to standing responses. Decreased LF power and LF/(LF + HF) and LF/HF ratios in DTC patients versus healthy controls indicated a sympathetic failure ascribed to the TSH-suppressive therapy with l-T4 rather than to direct effects of rhTSH.

CONCLUSIONS

These findings allowed us to confirm the cardiovascular safety of rhTSH and the absence of its effects on sympathovagal control of HRV when used in the follow-up of patients with normal heart function after thyroid ablation for DTC.

Can we Develop Neurally Acting Drugs for the Treatment of Migraine?

Serotonin (5-HT)(1B/1D) receptor agonists, which are also known as triptans, represent the most important advance in migraine therapeutics in the four millennia that the condition has been recognized. The vasoconstrictive activity of triptans produced a small clinical penalty in terms of coronary vasoconstriction but also raised an enormous intellectual question: to what extent is migraine a vascular problem? Functional neuroimaging and neurophysiological studies have consistently developed the theme of migraine as a brain disorder and, therefore, demanded that the search for neurally acting antimigraine drugs should be undertaken. The prospect of non-vasoconstrictor acute migraine therapies, potential targets for which are discussed here, offers a real opportunity to patients and provides a therapeutic rationale that places migraine firmly in the brain as a neurological problem, where it undoubtedly belongs.

Role of the immune system in chronic pain

During the past two decades, an important focus of pain research has been the study of chronic pain mechanisms, particularly the processes that lead to the abnormal sensitivity - spontaneous pain and hyperalgesia - that is associated with these states. For some time it has been recognized that inflammatory mediators released from immune cells can contribute to these persistent pain states. However, it has only recently become clear that immune cell products might have a crucial role not just in inflammatory pain, but also in neuropathic pain caused by damage to peripheral nerves or to the CNS.

Role of nitric oxide in Parkinson's disease

As a signal molecule, nitric oxide (NO) plays an important role in a variety of signal transduction pathways that are crucial for maintaining the physiologic functions of vascular, respiratory, immune, muscular, and nervous systems. NO and its derivatives are also involved in the pathogenic processes in various types of diseases including, but not limited to, neurodegenerative disorders. Although the molecular mechanisms of how NO contributes to diseases are not completely understood, studies have shown that NO may cause neuronal injury and death by mediation of excitotoxicity, damage of DNA, and/or modification of proteins. Understanding the pathogenic mechanisms of NO and its role in Parkinson's disease (PD) and other neurodegenerative diseases may help to develop novel neuroprotective therapies for these diseases.

Calcitonin gene-related peptide and its role in migraine pathophysiology

Migraine is a common neurological disorder that is associated with an increase in plasma calcitonin gene-related peptide (CGRP) levels. CGRP, a neuropeptide released from activated trigeminal sensory nerves, dilates intracranial blood vessels and transmits vascular nociception. Therefore, it is propounded that: (i) CGRP may have an important role in migraine pathophysiology, and (ii) inhibition of trigeminal CGRP release or CGRP-induced cranial vasodilatation may abort migraine. In this regard, triptans ameliorate migraine headache primarily by constricting the dilated cranial blood vessels and by inhibiting the trigeminal CGRP release. In order to explore the potential role of CGRP in migraine pathophysiology, the advent of a selective CGRP receptor antagonist was obligatory. The introduction of di-peptide CGRP receptor antagonists, namely BIBN4096BS (1-piperidinecarboxamide, N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl] pentyl] amino]-1-[(3,5-dibromo-4-hydroxyphenyl) methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl)-, [R-(R*,S*)]-), is a breakthrough in CGRP receptor pharmacology and can be used as a tool to investigate the role of CGRP in migraine headaches. Preclinical investigations in established migraine models that are predictive of antimigraine activity have shown that BIBN4096BS is a potent CGRP receptor antagonist and that it has antimigraine potential. Indeed, a recently published clinical study has reported that BIBN409BS is effective in treating acute migraine attacks without significant side effects. The present review will discuss mainly the potential role of CGRP in the pathophysiology of migraine and the various treatment modalities that are currently available to target this neuropeptide.

New targets in the acute treatment of headache

PURPOSE OF REVIEW

The aim of this article is to review recently identified targets for the acute treatment of primary headache disorders.

RECENT FINDINGS

Calcitonin gene-related peptide (CGRP) receptor blockade has been shown to be an effective acute anti-migraine strategy and is a non-vasoconstrictor in terms of the mechanism of action. It is likely that direct blockade of CGRP release by inhibition of trigeminal nerves would be similarly effective in both migraine and cluster headache. Options for acute treatment based on preclinical work and initial clinical studies include: serotonin 5HT1F and 5HT1D receptor agonists, glutamate excitatory amino acid receptor antagonists, nitric oxide synthase inhibitors and adenosine A1 receptor agonists. Proof of principle studies with octreotide, a somatostatin receptor agonist, demonstrated it to be better than placebo in the acute treatment of cluster headache but not in the acute management of migraine.

SUMMARY

The prospect of a non-vasoconstrictor acute migraine therapy offers a real opportunity to patients, and perhaps more importantly, provides a therapeutic rationale to plant migraine and cluster headache firmly in the brain as neurological problems.

Nonpharmacologic treatment of migraine

Nonpharmacologic treatment of migraine is often used by patients and can provide interesting options for physicians. Knowledge about the evidence and its absence is important. Avoidance of trigger factors can help, if individualized. Behavioral approaches, such as relaxation techniques, biofeedback, and cognitive-behavioral therapy, require far more specialist time or technical devices, but are supported by some evidence, which is mostly old. The same is true for hypnosis. A new approach in migraine prevention is aerobic exercise, which is associated with positive side effects. Whether it will take a strong role, similar to the treatment of depression, remains to be seen. There is no convincing evidence for the efficacy of spinal manipulation. Hyperbaric oxygen may be an effective, but rarely practical prophylactic measure. The evidence pertaining to the efficacy of acupuncture is controversial because of methodologic difficulties, but an ongoing large German study may provide valuable evidence in the near future. Nutritional supplements acting on mitochondrial metabolism, such as magnesium, riboflavin, and coenzyme Q10, were shown to be effective in small, randomized, controlled trials. More studies on the different therapeutic interventions are needed, using modern diagnostic standards and state-of-the-art trial methodology.

Etiology of primary headaches: the importance of genes and environment

Results from twin studies show that genes play an important role for susceptibility to migraine. The propensity for migraine to run in some families but not in others arises predominantly from alleles shared by family members and not the shared family environment, and that environmental influences on migraine are unique to the affected family member. The main genetic and environmental architecture for the other two major primary headaches, tension-type and cluster, remains to be elucidated. This review focuses on recent advances in twin studies of primary headaches and the future prospects are outlined.

L-arginine, the natural precursor of NO, is not effective for preventing bone loss in postmenopausal women

NO is an important regulator of bone turnover. L-Arginine, the natural precursor of NO, can enhance NO production. However, no effect of L-arginine hydrochloride supplementation was found on bone metabolism or on BMD, bone mass, or bone structure of healthy postmenopausal women.

INTRODUCTION

Recent studies indicate that NO exerts an anabolic effect on bone cell activity. The NO level of the human body can be elevated by administering pharmacological NO donors. Animal studies and the first human trial showed that NO donor administration had a positive effect on bone formation and a negative effect on bone resorption. L-arginine, the natural precursor of NO, can enhance NO production. This study was conducted to examine the effect of an oral L-arginine supplement on bone metabolism of healthy postmenopausal women.

MATERIALS AND METHODS

The participants in this study were 30 healthy, age-matched postmenopausal women, divided into two groups. For 6 months, one group (54.5 +/- 4.1 years; 66.3 +/- 10.5 kg) received a daily oral supplement with 18 g L-arginine hydrochloride (14.8 g free L-arginine). The other 15 volunteers (55.3 +/- 4.4 years; 64.2 +/- 9.1 kg) received 18 g dextrose as a placebo. To verify compliance, 24-h urinary excretion of nitrogen was analyzed for 2 consecutive days at baseline and after 2, 4, and 6 months. At baseline and after 2, 4, and 6 months of supplementation, blood was drawn for analysis of insulin-like growth factor-I (IGF-I) and biomarkers of bone metabolism. At baseline, after 6 months, and after 1 year, pQCT measurements were performed at trabecular and cortical sites of the radius and tibia. The two groups of subjects were compared by repeated measures ANOVA.

RESULTS

As expected, in the group with L-arginine hydrochloride supplementation, nitrogen excretion rose, and in the placebo group, it remained constant. Only bone formation marker, procollagen type I propeptides (PICP), increased significantly (p < 0.05) after 6 months of L-arginine supplementation. The results from pQCT showed no significant changes at any site in either group. No significant change in IGF-I concentration, which might have been caused by the L-arginine hydrochloride supplementation, was evident.

CONCLUSIONS

We conclude from these results that supplementation with L-arginine hydrochloride is not effective for improving bone mass in humans.

Sensory nitrergic meningeal vasodilatation and non-nitrergic plasma extravasation in anaesthesized rats

The aim of the present study was to evaluate the role of nitric oxide (NO) of sensory neural origin in neurogenic inflammatory response in the trigeminovascular system. Antidromic vasodilatation and plasma extravasation in response to electrical stimulation (15 V, 5 Hz, 0.5 ms, 100 impulses) of the trigeminal ganglion were investigated in the dura mater and nasal mucosa/upper eyelid by laser Doppler flowmetry and [(125)I]-labelled bovine serum albumin, respectively. Electrical stimulation of the trigeminal ganglion of rats elicited a reproducible ipsilateral enhancement of both meningeal and nasal mucosal blood flow. N(omega)-nitro-L-arginine (L-NNA; 4, 8, and 16 mg/kg, i.v.), a nonselective inhibitor of nitric oxide synthase (NOS), inhibited antidromic vasodilatation both in the dura mater (15.86+/-2.05%, 22.82+/-2.51%, and 36.28+/-4.37%) and nasal mucosa (35.46+/-8.57%, 58.72+/-9.2%, and 89.99+/-8.94%) in a dose-dependent manner. Specific inhibitors of neuronal NOS, 7-nitroindazole (7-NI; 20 mg/kg, i.v.) and 3-bromo-7-nitroindazole (3Br-7NI; 10 mg/kg, i.v.) were administered to assess the possible role of NO released from the trigeminal sensory fibres. The meningeal vasodilatation was inhibited by both 3Br-7NI and 7-NI (63.36+/-7.7% and 49+/-6.5%, respectively). The nasal hyperaemic response was also reduced by 3Br-7NI (78.26+/-8.7%). Plasma extravasation in the dura mater and upper eyelid evoked by electrical stimulation of the trigeminal ganglion (25 V, 5 Hz, 0,5 ms, 5 min), expressed as extravasation ratios (ERs) of the stimulated vs. nonstimulated sides, was 1.80+/-0.8 and 4.63+/-1.24, respectively. This neurogenic oedema formation was not inhibited by neither L-NNA nor 3Br-7NI. It is concluded that neural nitrergic mechanisms are involved in the meningeal vasodilatation evoked by electrical stimulation of the trigeminal ganglion.

Glyceryl trinitrate triggers premonitory symptoms in migraineurs

Studying attacks of migraine is considerably hampered by its fundamentally episodic nature. Developing approaches to triggering migraine reliably is important for advancing understanding of the disorder by facilitating its study. Based on the work of the Copenhagen Group we administered an intravenous infusion of 0.5 microg/kg/min glyceryl trinitrate (GTN) to 44 migraineurs, 23 migraine without aura, 21 migraine with aura, and to 12 healthy controls. We sought to characterise the GTN-induced migraine in terms of the clinical features of the attacks and reproducibility of triggering, and included a non-migraine control group for the purpose of comparing any effects to exclude an ordering effect. Of the 44 patients administered GTN, 33 had a migraine attack fulfilling International Headache Society criteria. Thirty-two attacks were of migraine without aura and one of migraine with aura. Twelve patients described typical premonitory symptoms, which have not been previously documented with GTN-induced migraine. A repeat attack was triggered in all subjects but one. In one case a visual aura was also triggered both times. Our study shows that GTN-induced triggering is common in our patients, and remarkably reproducible. The data will facilitate the use of the GTN model in studies requiring extensive planning, such as brain imaging, or where preventive questions are at issue. We also report the first patient with a reproducible GTN-triggered migraine with aura.

[What is needed to develop a headache? Anatomical and pathophysiological implications]

The shared anatomical and physiological substrate for headache syndromes is the neural innervation of the cranial circulation. Evidence suggests, that the observed dilatation of vessels in trigeminal pain is not inherent to a specific headache syndrome but rather a feature of the physiology of the trigeminal neural innervation of the cranial circulation. Moreover, the impact of vascular changes for the generation of headaches remains elusive. The trigeminal nerve innervates blood vessels within ipsilateral meninges. Upon activation neuropeptides such as CGRP are released. Blockade of both the trigeminal nerve system and neuropeptides are crucial targets for headache alleviating drugs. While these mechanisms are well known the events within and outside the CNS which initiate headaches are poorly understood. This article will review the anatomy and physiology of the trigeminovascular system which demand renewed consideration of the neural influences in many primary headaches.

Periods of cluster headache induced by nitrate therapy and spontaneous remission of angina pectoris during active clusters

Glyceryl trinitrate (GTN) is known to induce single extra attacks of cluster headache (CH) during active cluster periods, most probably via actions of nitric oxide (NO). Induction of whole periods of CH by organic nitrates has, however, attracted little attention in the literature. We report on eight patients with episodic CH and coexistent effort-induced angina pectoris. Cases 1-6 had been free of their headaches for many years but got recurrence of CH within a few weeks after the administration of long-acting organic nitrates (isosorbide-dinitrate, isosorbide-5-mononitrate or slow-release GTN) aimed at treating their chest pains. These nitrate-induced headache periods were more severe and had a longer duration than the previous spontaneous ones. Furthermore, one of the subjects and two additional cases experienced a marked reduction of their anginal attacks during successive CH periods. Exercise time to effort-induced angina was increased in all three patients and one of them revealed a markedly elevated threshold for eliciting ischaemic cardiac symptoms by standardized physical exercise on a cycle ergometer. We hypothesize whether extra CH periods elicited by sustained nitrate therapy and remission of angina pectoris during active clusters are caused by central mechanisms involving inhibition of sympathetic tone and effects on both cranial vessels and cardiac functions.

Changes in Cortical Dynamics in the Preictal Stage of a Migraine Attack

Neurophysiologic studies suggest that migraineurs without aura have a dysfunction of cortical information processing in the pain-free interval. In this study, the advanced method of nonlinear multielectrode sleep-EEG analysis is used to investigate changes of cortical activity in the preictal time span. Five patients (four women, one man; age range, 29 to 58 years) experiencing migraine without aura participated in the study. The patients spent two blocks in the sleep laboratory. The first block was taken in a headache-free interictal time interval, and the second block when the onset of a migraine attack was most likely. After a nocturnal migraine attack, the patient was asked to mark the maximum of migraine pain in a surface-head scheme. The comparison of preictal and interictal EEGs enabled the authors to obtain a topographical view of changes in cortical dynamics. In each patient map, an area was found that displayed a pronounced focus indicating the region of maximum change in dimensional complexity. It shows a clearly recognizable correspondence with the scalp topography of the later pain perception. These findings indicate an association between cortical status and pain lateralization in the preictal time span.

Reliability of the nitroglycerin provocative test in the diagnosis of neurovascular headaches

Nitroglycerin administration provokes spontaneous-like migraine attacks in migraine and cluster headache (CH) patients. Nitroglycerin-induced migraine-like headache has been used as an experimental model of migraine. In this paper, we evaluate the possibility of using the nitroglycerin provocative test (NPT) as a supportive measure in the diagnosis of primary neurovascular headaches by assessing its reliability on a large population and adopting strict criteria for rating the response as positive or negative. Our population consisted of 197 migraineurs, 42 subjects suffering from cluster headache and 53 healthy controls. In migraine without aura, the test sensitivity was 82.1%, specificity 96.2% and accuracy 85.5%, while in subjects suffering from migraine with aura, the reliability of the NPT was less satisfactory (sensitivity 13.6%, specificity 96.2% and accuracy 72%). In CH patients tested during the active phase of the disease the sensitivity was 80.6%, specificity 100% and accuracy 92.9%. NPT is an easy, low-cost and reliable method for supporting the diagnosis of migraine without aura and cluster headache.

Circulating nitric oxide is modulated by recombinant human TSH administration during monitoring of thyroid cancer remnant

During the administration of recombinant human TSH (rhTSH) to monitor differentiated thyroid carcinoma, mild side effects, such as nausea and headaches, often occur. The origin of these is not clear. Since changes in TSH and thyroid hormones can modulate some endothelial-derived factors, we aimed at testing whether rhTSH administration induces changes in nitric oxide. We studied 25 patients (56.6+/-12.6 yr) who had undergone thyroidectomy followed by ablative radioiodine for papillary thyroid cancer and who were under follow-up. While L-thyroxine therapy continued, thyroglobulin (Tg), TSH, free-T3, free-T4 and nitrite-plus-nitrate (NOx) concentrations were evaluated before and after rhTSH administration (0.9 mg i.m. on 2 consecutive days). Mean TSH showed a huge increase from baseline (0.1+/-0.0 mIU/l) to day 3 (216.3+/-17.5 mIU/l, p<0.001), which was not accompanied by changes in thyroid hormones. Mean baseline NOx levels were 12.6+/-1.2 micromoles/l and showed a significant increase on day 3 (20.1+/-1.2 micromoles/l, p<0.05 vs day 0), followed by progressive reduction from day 6 (18.1+/-2.8 micromoles/l) to day 9 (10.6+/-1.3 micromoles/l, p<0.05 vs day 0). There was a significant (p=0.04) correlation between the percentage increase in TSH and the percentage increase in NOx. On the other hand, increase in TSH did not correlate with the percentage decrease in NOx from day 6 to day 9. No correlation was noted between the increase in TSH or NOx and the occurrence or severity of the symptoms. Our study shows that, during rhTSH testing, circulating nitric oxide increases. This endothelial-derived factor might, in turn, mediate the occurrence of vasomotor headache and nausea in some particularly susceptible patients.

Structural characterization and kinetics of nitric-oxide synthase inhibition by novel N5-(iminoalkyl)- and N5-(iminoalkenyl)-ornithines

Isoform-specific nitric-oxide synthase (NOS) inhibitors may prove clinically useful in reducing the pathophysiological effects associated with increased neuronal NOS (nNOS) or inducible NOS (iNOS) activity in a variety of neurological and inflammatory disorders. Analogs of the NOS substrate L-arginine are pharmacologically attractive inhibitors because of their stability, reliable cell uptake, and good selectivity for NOS over other heme proteins. Some inhibitory arginine analogs show significant isoform selectivity although the structural or mechanistic basis of such selectivity is generally poorly understood. In the present studies, we determined by x-ray crystallography the binding interactions between rat nNOS and N5-(1-imino-3-butenyl)-L-ornithine (L-VNIO), a previously identified mechanism-based, irreversible inactivator with moderate nNOS selectivity. We have also synthesized and mechanistically characterized several L-VNIO analogs and find, surprisingly, that even relatively minor structural changes produce inhibitors that are either iNOS-selective or non-selective. Furthermore, derivatives having a methyl group added to the butenyl moiety of L-VNIO and L-VNIO derivatives that are analogs of homoarginine rather than arginine display slow-on, slow-off kinetics rather than irreversible inactivation. These results elucidate some of the structural requirements for isoform-selective inhibition by L-VNIO and its related alkyl- and alkenyl-imino ornithine and lysine derivatives and may provide information useful in the ongoing rational design of isoform-selective inhibitors.

Prophylactic Therapy for Migraine

The term migraine is derived from the ancient Greek word hemicrania introduced by Galen in approximately 200 AD. However, descriptions of "sick headache" have been found dating back to as far as 3000 BC. Despite this, migraine is a condition that still remains underdiagnosed and undertreated. The development of effective abortive agents, such as the triptans, have had a significant impact on migraine management, but there still remains a substantial proportion of migraineurs in whom further medication is required in the form of preventatives. These have the potential to transform the lives of many migraine sufferers.

Agonist actions of dihydroergotamine at 5-HT2B and 5-HT2C receptors and their possible relevance to antimigraine efficacy

1. The pharmaceutical compound, dihydroergotamine (DHE) is dispensed to prevent and reduce the occurrence of migraine attacks. Although still controversial, the prophylactic effect of this drug is believed to be caused through blockade and/or activation of numerous receptors including serotonin (5-HT) receptors of the 5-HT2 subtype. 2. To elucidate if 5-HT2 receptors (5-HT2Rs) may be involved in DHE prophylactic effect, we performed investigations aimed to determine the respective pharmacological profile of DHE and of its major metabolite 8'-hydroxy-DHE (8'-OH-DHE) at the 5-HT2B and 5-HT2CRs by binding, inositol triphosphate (IP3) or cyclic GMP (cGMP) coupling studies in transfected fibroblasts. 3. DHE and 8'-OH-DHE are competitive compounds at 5-HT2B and 5-HT2CRs. 8'-OH-DHE interaction at (5-HT2BRs) was best fitted by a biphasic competition curve and displayed the highest affinity with a Ki of 5 nm. These two compounds acted as agonists for both receptors in respect to cGMP production with pEC50 of 8.32+/-0.09 for 8'-OH-DHE at 5-HT2B and 7.83+/-0.06 at 5-HT2CRs. 4. Knowing that the antimigraine prophylactic effect of DHE is only observed after long-term treatment, we chronically exposed the recombinant cells to DHE and 8'-OH-DHE. The number of 5-HT2BR-binding sites was always more affected than 5-HT2CRs. At 5-HT2BRs, 8'-OH-DHE was more effective than DHE, with an uncoupling that persisted for more than 40 h for IP3 or cGMP. By contrast, the 5-HT2CR coupling was reversible after either treatment. 5. Chronic exposure to 8'-OH-DHE caused a persistent agonist-mediated desensitisation of 5-HT2B, but not 5-HT2CRs. This may be of relevance to therapeutic actions of the compound.

Nitric oxide pathway and response to nitroglycerin in cluster headache patients: plasma nitrite and citrulline levels

Nitric oxide (NO) may participate in the mechanisms underlying vascular headaches, such as migraine and cluster headache (CH), by triggering neurogenic inflammation and activation of fibres conveying nociceptive inputs to the trigeminal ganglion. Similarly to migraine, the administration of the NO donor glyceryltrinitrate (GTN) to CH patients is a known model of inducing spontaneous-like attacks. We carried out a GTN test (0.9 mg, sublingually) in 18 patients with episodic CH in active phase and 12 controls. The plasma levels of NO metabolite nitrites (NO2-), after conversion of nitrates to NO2-, were measured spectrophotometrically at baseline, at the maximum intensity of the induced response (or 45 min after GTN in controls), and 120 min after GTN administration. The basal plasma levels of L-citrulline were also assayed in patients and controls using high-performance liquid chromatography. Basal NO2- levels, similar in GTN-responsive patients and controls (48.3 +/- 10.6 and 44.6 +/- 9.5 micromol/l, respectively) were found to be increased significantly at pain peak in patients (76.1 +/- 10.2 micromol/l) and after 45 min in controls (78.2 +/- 9.6 micromol/l) (P < 0.01 vs. respective baseline values), but not after 120 min, without differences between groups. L-citrulline levels in basal conditions showed no differences between groups (patients 64.8 +/- 11.7, controls 67.3 +/- 10.8 micromol/l). These data do not support the presence of a basal hyperactivity of the L-arginine-NO pathway in CH patients. Increased NO production may be of importance in the mechanisms leading to CH attacks, but other factors are likely to render CH patients hyperresponsive to NO, and ultimately to cause the occurrence of pain and associated features.

Peripheral and central mechanisms in tension-type headache: an update

Despite the tremendous socioeconomic impact of tension-type headache surprisingly little is known about the underlying pathophysiology and treatment. Existing evidence and theories about the relation between central and peripheral mechanisms are discussed. Central sensitization is probably the most important key to understand this widespread disorder. An effective prevention or reversal of this central sensitization will probably be of major importance in future treatment strategies.

Pathophysiology, epidemiology, and impact of migraine

Despite a decade of progress, migraine headache remains prevalent, disabling, underdiagnosed, and undertreated in the United States. Migraine affects approximately 12% of the population, and the economic burden in terms of annual cost of labor lost to migraine disability is between $5.6 and $17.2 billion. The threshold for migraine may be genetically determined, although recent genetic and neurophysiologic studies point to migraine as possibly a channelopathy. Cerebral cortical and brain stem changes occur in migraine. Head pain and associated symptoms of migraine can be explained by activation of the trigeminal vascular system. Evidence has also been accumulated that suggests the release of nitric oxide is an important trigger mechanism. Introduction of the triptans has dramatically advanced acute migraine pharmacotherapy, and preventive therapy has greatly improved; however, public health initiatives may be needed to further advance diagnosis and treatment of this common and disabling disorder.

Nalpha-methylhistamine safety and efficacy in migraine prophylaxis: phase I and phase II studies

OBJECTIVE

To study the therapeutic potential of the subcutaneous administration of Nalpha-methylhistamine in migraine prophylaxis.

BACKGROUND

The histamine catabolite, Nalpha-methylhistamine, possesses a selective affinity for H3 receptors. We consequently considered it viable to conduct a clinical pharmacological study to evaluate the safety and efficacy of this histaminergic H3 agonist in migraine prophylactic treatment, which specifically may inhibit the neurogenic edema response involved in migraine pathophysiology.

METHODS

Phase I.-In a clinical trial of 30 healthy volunteers, the effects of the subcutaneous administration of Nalpha-methylhistamine and placebo were studied to assess undesirable symptomatic effects. Phase II.-In a clinical open study, we evaluated the efficacy of Nalpha-methylhistamine in reducing headache intensity, frequency, and duration; and in decreasing analgesic intake in 18 patients with migraine.

RESULTS

Phase I.-None of the variables studied showed significant differences (P>.05), and no secondary effects were observed at doses below 10 ng. Phase II.-Nalpha-methylhistamine, at doses of 1 to 3 ng, significantly reduced (P<.0001) the frequency, intensity, and duration of migraine attacks, as well as the need for rescue analgesics. However, at doses greater than 3 ng, patients experienced intense headache.

CONCLUSIONS

The present study provides evidence of the safety and efficacy of Nalpha-methylhistamine applied subcutaneously at doses of 1 to 3 ng twice a week.

Capsaicin receptor immunoreactivity in the human trigeminal ganglion

The cloned capsaicin receptor, also known as vanilloid receptor subtype 1 (VR1) receptor, has been demonstrated to be an integral membrane protein with homology to a family of putative store-operated calcium channels. The VR1 receptor is activated not only by capsaicin but also by noxious heat and protons, and therefore it is suggested as a molecular integrator of chemical and physical stimuli that elicit pain. In the present study, indirect immunofluorescence detected a small number of neurons that are VR1 receptor immunoreactive (ir) (171 versus 1038 or 16% of all neuronal cell bodies) in the human trigeminal ganglion (TG). In addition, RT-PCR confirmed the presence of VR1 mRNA in the human TG. It has been hypothesized that TG neuronal cell bodies are the source of capsaicin-stimulated release of calcitonin gene-related peptide (CGRP), and hence co-localization experiments were performed. Around 10% of the VR1 receptor-ir is expressed on neurons that contain CGRP-ir (ten among 74) in the human TG, indicating that capsaicin may act through the VR1 receptor to modulate the release of CGRP and in turn to modulate pain. We observed that 8% of the VR1 receptor-ir neuronal cell bodies contain substance P-ir and 5% nitric oxide synthase. Capsaicin can release nitric oxide, CGRP and substance P from sensory nerves and contribute to central sensitization.

Cortical spreading depression and gene regulation: relevance to migraine

Cortical spreading depression (CSD) may be the underlying mechanism of migraine aura. The role of CSD in initiating a migraine headache remains to be determined, but it might involve specific changes in gene expression in the brain. To examine these changes, four episodes of CSD at 5-minute intervals were induced in the mouse brain by application of 300mM KCl, and gene expression was examined 2 hours later using cDNA array and reverse transcriptase-polymerase chain reaction. Controls consisted of groups that received anesthesia only, attachment of recording electrodes only, and application of 0.9% NaCl. Of the over 1,180 genes examined in our experiments, those consistently regulated by CSD included vasoactive peptides; the vasodilator atrial natriuretic peptide was induced by CSD, while the vasoconstrictor neuropeptide Y was downregulated. Other genes specifically regulated by CSD were involved in oxidative stress responses (major prion protein, glutathione-S-transferase-5, and apolipoprotein E). L-type calcium channel mRNA was upregulated. In summary, CSD regulates genes that are intrinsic to its propagation, that identify accompanying vascular responses as a potential source of pain, and that protect against its potential pathological consequences. We believe these observations have strong relevance to the mechanisms of migraine and its outcomes.