Variations in the platelet arginine/nitric oxide pathway during the ovarian cycle in females affected by menstrual migraine

Migraine Attacks Triggered by Ingestion of Watermelon

INTRODUCTION

Ingesting some foods can trigger headache attacks in migraine patients. Diet-sourced citrulline activates the l-arginine-nitric oxide pathway, acting on the pathophysiology of migraine.

METHODS

The study was a clinical trial, interventional, controlled, and with group comparison. The sample was non-random, composed of 38 volunteers with migraine and 38 without headache (control). Both groups ingested a portion of watermelon to determine the onset of headache attacks. Before and after ingesting watermelon, they underwent blood collections to determine serum nitrite levels.

RESULTS

There were 38 volunteers diagnosed with migraine without aura and 38 controls, whose mean age was, respectively, 22.4 ± 1.5 and 22.9 ± 3.1 years (p = 0.791). Headache was triggered by watermelon ingestion after 124.3 ± 20.5 min of ingestion in 23.7% (9/38) of the migraine volunteers and in none of the controls (p = 0.002). There was an increase in serum nitrite levels, both in migraine volunteers (23.4%) and in the control group (24.3%), after watermelon ingestion. This difference was significant (p < 0.001).

DISCUSSION

Watermelon ingestion triggered headache attacks in migraine patients and increased serum nitrite levels, attesting to a possible activation of the l-arginine-nitric oxide pathway.

Gender-related differences in migraine

Migraine is considered mostly a woman’s complaint, even if it affects also men. Epidemiological data show a higher incidence of the disease in women, starting from puberty throughout life. The sex-related differences of migraine hold clinical relevance too. The frequency, duration, and disability of attacks tend to be higher in women. Because of this, probably, they also consult specialists more frequently and take more prescription drugs than men. Different mechanisms have been evaluated to explain these differences. Hormonal milieu and its modulation of neuronal and vascular reactivity is probably one of the most important aspects. Estrogens and progesterone regulate a host of biological functions through two mechanisms: nongenomic and genomic. They influence several neuromediators and neurotransmitters, and they may cause functional and structural differences in several brain regions, involved in migraine pathogenesis. In addition to their central action, sex hormones exert rapid modulation of vascular tone. The resulting specific sex phenotype should be considered during clinical management and experimental studies.

Suppression of Menstrual-Related Migraine Attack Severity Using Pyridoxine, Thiamine, and Cyanocobalamin: A Quasi-Experimental Within-Subject Design

Background: B-group vitamins can potentially contribute to migraine prophylaxis through various mechanisms. We conducted a quasi-experimental study to assess the efficacy and tolerability of a combination of vitamins B1, B6, and B12 (Neurobion) for prophylaxis of menstruation-related migraine attacks. Methods: Women diagnosed with menstrual-related migraine, both chronic and episodic headaches, were enrolled. The patients began Neurobion therapy one week before the menstruation cycle, and repeated the injection for three consecutive months; each ampoule contained 100 mg of vitamins B1 and B6 as well as 1000 μg of vitamin B12. Neurobion was used as an add-on therapy for patients receiving the same prophylactic therapy during the last two months before the start of the study. The outcome parameter examined the severity of menstrual-related migraine attacks on a 10-point visual analog scale (VAS). Results: Three hundred eighty-three patients (169 with chronic migraine and 214 with episodic migraine) were included in the final analysis. The patients received treatment with a combination of vitamins B1, B6, and B12 with positive results. The mean intensity of menstrual-related migraine attacks was reduced from 6.7 on the 10-point VAS to 3.2 (P < 0.001) in patients with chronic migraine. The mean severity of menstrual-related migraine attacks was also reduced from 7.2 to 3.7 in patients with episodic migraine (P < 0.001). There was no significant difference in the reduction of headache severity between the two groups of migraineurs (P = 0.985). Conclusions: Neurotropic vitamins, including pyridoxine, thiamine, and cyanocobalamin yielded significant reductions in the severity of menstrual-related migraine attacks. Neurobion as a combination of vitamins B1, B6, and B12 appears to be well-tolerated and beneficial as an adjuvant in treatment and prophylaxis of menstrual-related migraine attacks. Further large-scale trials with long-term follow-up will be required to confirm our results.

An Association of Serotonin with Pain Disorders and Its Modulation by Estrogens

Ovarian hormones play an important role in pain perception, and are responsible, at least in part, for the pain threshold differences between the sexes. Modulation of pain and its perception are mediated by neurochemical changes in several pathways, affecting both the central and peripheral nervous systems. One of the most studied neurotransmitters related to pain disorders is serotonin. Estrogen can modify serotonin synthesis and metabolism, promoting a general increase in its tonic effects. Studies evaluating the relationship between serotonin and disorders such as irritable bowel syndrome, fibromyalgia, migraine, and other types of headache suggest a clear impact of this neurotransmitter, thereby increasing the interest in serotonin as a possible future therapeutic target. This literature review describes the importance of substances such as serotonin and ovarian hormones in pain perception and illustrates the relationship between those two, and their direct influence on the presentation of the aforementioned pain-related conditions. Additionally, we review the pathways and receptors implicated in each disorder. Finally, the objective was to stimulate future pharmacological research to experimentally evaluate the potential of serotonin modulators and ovarian hormones as therapeutic agents to regulate pain in specific subpopulations.

Neurovascular contributions to migraine: Moving beyond vasodilation

Migraine is the third most common disease worldwide, the most common neurological disorder, and one of the most common pain conditions. Despite its prevalence, the basic physiology and underlying mechanisms contributing to the development of migraine are still poorly understood and development of new therapeutic targets is long overdue. Until recently, the major contributing pathophysiological event thought to initiate migraine was cerebral and meningeal arterial vasodilation. However, the role of vasodilation in migraine is unclear and recent findings challenge its necessity. While vasodilation itself may not contribute to migraine, it remains possible that vessels play a role in migraine pathophysiology in the absence of vasodilation. Blood vessels consist of a variety of cell types that both release and respond to numerous mediators including growth factors, cytokines, adenosine triphosphate (ATP), and nitric oxide (NO). Many of these mediators have actions on neurons that can contribute to migraine. Conversely, neurons release factors such as norepinephrine and calcitonin gene-related peptide (CGRP) that act on cells native to blood vessels. Both normal and pathological events occurring within and between vascular cells could thus mediate bi-directional communication between vessels and the nervous system, without the need for changes in vascular tone. This review will discuss the potential contribution of the vasculature, specifically endothelial cells, to current neuronal mechanisms hypothesized to play a role in migraine. Hypothalamic activity, cortical spreading depression (CSD), and dural afferent input from the cranial meninges will be reviewed with a focus on how these mechanisms can influence or be impacted by blood vessels. Together, the data discussed will provide a framework by which vessels can be viewed as important potential contributors to migraine pathophysiology, even in light of the current uncertainty over the role of vasodilation in this disorder.

Neuronal Nitric Oxide Synthase (nNOS, NOS1) rs693534 and rs7977109 Variants and Risk for Migraine

BACKGROUND/OBJECTIVES

Many biochemical, pharmacological, neuropathological, and experimental data suggest a possible role of nitric oxide in the pathogenesis of migraine. We investigated the possible association between functional single nucleotide polymorphisms (SNPs) in the neuronal nitric oxide synthase gene (NOS1 or nNOS; chromosome 12q24.22) and the risk for migraine.

METHODS

We studied the frequency of the of rs7977109 and rs693534 genotypes and allelic variants in 197 patients with migraine and 308 healthy controls using a TaqMan-based qPCR assay. As a secondary analysis, we studied the possible influence of gender, age at onset of migraine, positive family history of migraine, and presence or absence of aura on the genotypes frequency.

RESULTS

The frequencies of rs7977109 and rs693534 genotypes and allelic variants were not associated with the risk for migraine with OR for minor alleles = 0.94 (95% CI 0.72-1.23) and = 0.88 (0.68-1.15), respectively, and the lack of association was not influenced by gender, age at onset of migraine, positive family history of migraine, and presence or absence of aura.

CONCLUSION

NOS1 rs7977109 and rs693534 genotypes and allelic variants are not associated with the risk for migraine in Caucasian Spanish people.

A cyclic pain: the pathophysiology and treatment of menstrual migraine

Catamenial migraine is a headache disorder occurring in reproductive-aged women relevant to menstrual cycles. Catamenial migraine is defined as attacks of migraine that occurs regularly in at least 2 of 3 consecutive menstrual cycles and occurs exclusively on day 1 to 2 of menstruation, but may range from 2 days before (defined as -2) to 3 days after (defined as +3 with the first day of menstruation as day +1). There are 2 subtypes: the pure menstrual migraine and menstrually related migraine. In pure menstrual migraine, there are no aura and no migraine occurring during any other time of the menstrual cycle. In contrast, menstrually related migraine also occurs in 2 of 3 consecutive menstrual cycles, mostly on days 1 and 2 of menstruation, but it may occur outside the menstrual cycle. Catamenial migraine significantly interferes with the quality of life and causes functional disability in most sufferers. The fluctuation of estrogen levels is believed to play a role in the pathogenesis of catamenial migraine. In this review, we discuss estrogen and its direct and indirect pathophysiologic roles in menstrual-related migraine headaches and the available treatment for women.

TARGET AUDIENCE

Obstetricians and gynecologists, family physicians.

LEARNING OBJECTIVES

After completing this CME activity, physicians should be better able to discuss the pathophysiology of catamenial migraine, identify the risk factors for catamenial migraine among women, and list the prophylactic and abortive treatments for migraines.

Transdermal hormonal therapy in perimenstrual migraine: why, when and how?

Experimental and clinical evidence is strongly in favor of a role for estrogens in migraine. It is clear that estrogen fluctuations represent trigger factors for the attacks, while the resolution of these fluctuations (menopause) may be associated to the remission or, conversely, to the worsening of the disease. However, the exact mechanisms and mediators underlying the effects of estrogens in migraine are largely unknown. The exact mechanisms and mediators underlying the effects of estrogens in migraine are largely unknown. In this review, we summarize clinical and preclinical data that are relevant for the role of estrogens in migraine and we discuss how estrogen modulation can be exploited positively to improve hormonal-related migraine.

Migraine in women: the role of hormones and their impact on vascular diseases

Migraine is a predominantly female disorder. Menarche, menstruation, pregnancy, and menopause, and also the use of hormonal contraceptives and hormone replacement treatment may influence migraine occurrence. Migraine usually starts after menarche, occurs more frequently in the days just before or during menstruation, and ameliorates during pregnancy and menopause. Those variations are mediated by fluctuation of estrogen levels through their influence on cellular excitability or cerebral vasculature. Moreover, administration of exogenous hormones may cause worsening of migraine as may expose migrainous women to an increased risk of vascular disease. In fact, migraine with aura represents a risk factor for stroke, cardiac disease, and vascular mortality. Studies have shown that administration of combined oral contraceptives to migraineurs may further increase the risk for ischemic stroke. Consequently, in women suffering from migraine with aura caution should be deserved when prescribing combined oral contraceptives.

Endothelial function in migraine: a cross-sectional study

Background

Migraine has been associated with cardiovascular disorders. Endothelial dysfunction may be a mechanism underlying this association. The present study tested the hypothesis that endothelium-dependent vasodilation, basal endothelial nitric oxide release and endothelial fibrinolytic capacity are impaired in migraine patients.

Methods

Graded doses of sodium nitroprusside (SNP, 0.2 to 0.8 μg.min^-1.dL^-1 forearm), substance P (0.2 to 0.8 pmol.min^-1.dL^-1 forearm) and N^G-monomethyl-L-arginine (L-NMMA, 0.1 to 0.4 μmol.min^-1.dL^-1 forearm) were infused into the brachial artery of 16 migraine patients with or without aura during a headache-free interval and 16 age- and sex-matched subjects without a history of migraine. Forearm blood flow (FBF) was measured by strain-gauge venous occlusion plethysmography. Local forearm release of tissue plasminogen activator (t-PA) in response to substance P infusion was assessed using the arteriovenous plasma concentration gradient. Responses to infused drugs were compared between patients and matched controls by analysis of variance.

Results

In both migraine patients and control subjects, SNP and substance P caused a dose-dependent increase, and L-NMMA a dose-dependent decrease in FBF (P < 0.001 for all responses). In both groups, substance P caused an increase in t-PA release (P < 0.001). FBF responses and t-PA release were comparable between migraine patients and control subjects.

Conclusions

The absence of differences in endothelium-dependent vasodilation, basal endothelial nitric oxide production and stimulated t-PA release between migraine patients and healthy control subjects argues against the presence of endothelial dysfunction in forearm resistance vessels of migraine patients.

Hyperinsulinaemia in migraineurs is associated with nitric oxide stress

There is growing evidence that alterations in the insulin and glucose metabolism may be involved in the pathogenesis of migraine. Nitric oxide (NO) stress has been associated with migraine. However, the role of NO on the insulin and glucose metabolism in migraineurs has remained elusive to date. The aim of the present study was to investigate the insulin and glucose metabolism in migraineurs and to determine possible interactions with the NO pathway. One hundred and twenty non-obese probands participated in this study, including 48 migraineurs and 72 healthy volunteers. Various parameters of the NO pathway, glucose metabolism as well as body measurement parameters were determined. We found a highly significantly increased insulin and Homeostasis Model Assessment (HOMA)-index in migraine patients, whereas fasting glucose was decreased. Logistic regression revealed an odds ratio of 5.67 for migraine, when comparing the lowest with the highest quartile of HOMA. Multivariate analysis showed that HOMA, waist-to-length ratio and nitrite as parameters of NO stress were highly significantly correlated. We show here that hyperinsulinaemia is associated with migraine and, furthermore, is correlated with increased NO stress. These findings represent a new pathophysiological mechanism that may be of clinical relevance.

Increased nitric oxide stress is associated with migraine

Nitric oxide (NO) has been implicated in migraine attacks, but the role of NO in migraine remains unclear. We here hypothesize that increased NO in the headache-free period is associated with migraine. One hundred and thirty probands participated in this study. Various parameters of the NO pathway, such as nitrate, nitrite, arginine, citrulline, nitrosylated proteins, asymmetric dimethylarginine, symmetrical dimethylarginine, expression of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase and two polymorphisms of eNOS were investigated. We found significant increased nitrate and decreased nitrite levels in migraineurs in the headache-free period. Nitrate and nitrite levels showed a significant inverse correlation. Logistic regression revealed an odds ratio of 3.6 for migraine. Other parameters of the NO pathway were neither altered in migraineurs nor correlated with nitrate. We show here that migraine patients suffer under sustained increased nitrosative stress in the headache-free period, which is associated with a 3.6-fold higher risk for migraine.

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.

Ovarian Hormones and Migraine Headache: Understanding Mechanisms and Pathogenesis-Part 2

Migraine headache is strongly influenced by reproductive events that occur throughout the lifespan of women. Each of these reproductive events has a different "hormonal milieu," which might modulate the clinical course of migraine headache. Estrogen and progesterone can be preventative or provocative for migraine headache under different circumstances depending on their absolute serum levels, constancy of exposure, and types of estrogen/progesterone derivatives. Attacks of migraine with and without aura respond differently to changes in ovarian hormones. Clearly a greater knowledge of ovarian hormones and their effect on migraine is essential to a greater understanding of the mechanisms and pathogenesis of migraine headache.

Plasma levels of cAMP, cGMP and CGRP in sildenafil-induced headache

Sildenafil, a selective inhibitor of the cyclic guanosine monophosphate (cGMP) degrading phosphodiestrase 5 (PDE5), induced migraine without aura in 10 of 12 migraine patients and in healthy subjects it induced significantly more headache than placebo. The aim of the present study was to determine whether the pain-inducing effects of sildenafil would be reflected in plasma levels of important signalling molecules in migraine: cGMP, cyclic adenosine monophosphate (cAMP) and calcitonin gene-related peptide (CGRP). Ten healthy subjects (four women, six men) and 12 patients (12 women) suffering from migraine without aura were included in two separate double-blind, placebo-controlled, cross-over studies in which placebo or sildenafil 100 mg was administered orally. Plasma levels of CGRP, cAMP and cGMP were determined in blood from the antecubital vein. Despite the ability of sildenafil to induce headache and migraine, no significant differences in plasma levels of CGRP, cGMP and cAMP were detected after sildenafil compared with placebo. In conclusion, plasma levels of CGRP, cGMP and cAMP remain normal during sildenafil-induced headache or migraine. However, since previous studies indicate an important role of these signalling molecules, the present study questions whether cAMP and cGMP in peripheral blood can be used for monitoring pathophysiological events in headache and migraine mechanisms.

Molecular Mechanisms of Migraine

Migraine is a common complex disorder that affects a large portion of the population and thus incurs a substantial economic burden on society. The disorder is characterized by recurrent headaches that are unilateral and usually accompanied by nausea, vomiting, photophobia, and phonophobia. The range of clinical characteristics is broad and there is evidence of comorbidity with other neurological diseases, complicating both the diagnosis and management of the disorder. Although the class of drugs known as the triptans (serotonin 5-HT(1B/1D) agonists) has been shown to be effective in treating a significant number of patients with migraine, treatment may in the future be further enhanced by identifying drugs that selectively target molecular mechanisms causing susceptibility to the disease.Genetically, migraine is a complex familial disorder in which the severity and susceptibility of individuals is most likely governed by several genes that may be different among families. Identification of the genomic variants involved in genetic predisposition to migraine should facilitate the development of more effective diagnostic and therapeutic applications. Genetic profiling, combined with our knowledge of therapeutic response to drugs, should enable the development of specific, individually-tailored treatment.

Physiological changes in platelet aggregation and nitric oxide levels during menstrual cycle in healthy women

Hormonal levels, mainly those of estrogens, protect women from the appearance of cardiovascular diseases by an increasing nitric oxide (NO) activity. NO is an endogenous vasodilator and antiaggregating substance. We decided to investigate platelet function and plasma levels of nitric oxide during preovulatory and midluteal phases in young and healthy women with normal menstrual cycles (MCs). Nine young, healthy female subjects had recorded three consecutive MCs before entering this program. Platelet-rich plasma (PRP) was used for the determination of platelet aggregation and NO measurements. Moreover, platelet sensitivity to the inhibitory effect of exogenous NO was tested. The EC(50) of collagen showed no differences between the preovulatory (1.36+/-0.16 microg/mL) and the midluteal (1.31+/-0.08 microg/mL; P, NS) phases. However, the EC(90) during the preovulatory phase was higher (2.05+/-0.2 microg/mL) than during the midluteal phase (1.8+/-0.6 microg/mL). Plasma levels of NO were lower during the preovulatory phase (19.1+/-2 microM) in comparison to the midluteal phase (20.9+/-2.3 microM). Interestingly, the exogenous amount of NO to produce at least half of the inhibition of an EC(90) collagen-induced aggregation was higher at the preovulatory phase (323.3+/-60.9 nM) than during the midluteal phase (240.0+/-37.5 nM; P, NS). We propose that during the follicular phase platelets rather use NO produced by the endothelium; therefore, it is necessary to add more agonist to activate those, but it results in higher consumption of circulating NO, whereas during luteal-phase platelets are not able to use NO, requiring lower amounts of agonist and thus resulting in higher plasma levels of NO. This is an interesting fact in research on cardiovascular diseases of women.

Increased plasma nitrites in migraine and cluster headache patients in interictal period: basal hyperactivity of L-arginine-NO pathway?

Nitrite concentrations in plasma were investigated in a population of migraine and cluster headache patients and a group of healthy non-headache controls. A hundred migraine patients and 69 cluster headache patients in the interictal period, and 112 controls, were studied. Significantly higher nitrite concentrations were found in migraine patients, with and without aura, and cluster headache patients, in remission and cluster phase, than in controls. These findings suggest that a basal dysfunction in the L-arginine-NO pathway may be involved in the peripheral mechanisms predisposing subjects with neurovascular headaches to individual attacks.

Blood nitrite levels in patients with migraine during headache-free period

OBJECTIVE

To investigate blood nitrite levels after migraine attacks and to assess whether or not the change in nitric oxide levels observed during acute migraine persist after the attacks.

BACKGROUND

Involvement of nitric oxide has been suggested in the initiation of acute migraine. Recent studies have shown alteration in the platelet response and platelet nitrite levels during migraine attacks.

METHODS

Patients with migraine with aura and patients without aura were included in the study. The study was conducted on 50 patients with migraine and 90 healthy controls. Blood from the patients was collected at least 7 +/- 0.8 days after the last attack of migraine. Nitrite levels in the polymorphonuclear leukocytes, platelets, and plasma were estimated. Platelet aggregation response in some of these patients was also studied.

RESULTS

No significant change in the polymorphonuclear leukocyte, platelet, and plasma nitrite levels in patients with migraine compared to controls was observed. Patients with migraine with aura had significantly lower polymorphonuclear leukocyte nitrite levels compared to those without aura (P<.05). In addition, no significant difference in the adenosine diphosphate-induced platelet aggregation was observed in the migraineurs compared to the healthy controls.

CONCLUSIONS

Results obtained indicate that the platelet aggregation response and the blood nitrite levels were not altered significantly after an attack in the patients with migraine.

Cortical spreading depression produces increased cGMP levels in cortex and brain stem that is inhibited by tonabersat (SB-220453) but not sumatriptan

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.

Hyposerotonin-induced nitric oxide supersensitivity in the cerebral microcirculation

OBJECTIVE

To investigate the relationship between hyposerotonin and cranial microvascular responses to nitric oxide (NO).

BACKGROUND

Although the mechanism underlying NO supersensitivity in migraine is still unclear, an alteration of the serotonin system is a possible explanation.

METHODS

Wistar rats were divided into control and hyposerotonin groups. Serotonin was depleted by intraperitoneal injection with 300 mg/kg of para-chlorophenylalanine (PCPA), a tryptophan hydroxylase inhibitor. Three days after PCPA pretreatment, the animals were prepared for assessment of their NO-induced vasomotor response using glyceryl trinitrate (GTN: 8 to 10 mg/kg, intravenously) as an NO donor. Pial circulation was visualized by the intravital fluorescein videomicroscopic technique. Images of vessels at 0, 5, 15, 30, and 60 minutes post GTN infusion were digitized and measured. At the end of monitoring, the rat brains were removed for ultrastructural study of the brain microvessels.

RESULTS

Infusion of GTN produced dose-dependent pial arteriolar dilatation. This vasodilator effect was significantly increased in the PCPA-treated groups, especially at 30 and 60 minutes. The percentage change from baseline diameter at 30 minutes after the 8-mg/kg GTN infusion was 42.6 +/- 3.1 for the hyposerotonin group and 16.8 +/- 2.9 for the control group (P<.001). Electron microscopic study revealed that exposure to the NO donor produced considerable changes in cerebral microvessels, characterized by focal ballooning of endothelial cells, increased microvillous formation, and increased endothelial pinocytosis. These anatomical changes were significantly more prominent in the hyposerotonin group.

CONCLUSIONS

A hyposerotoninergic condition can facilitate the NO-induced physiological and pathological responses in meningeal and cerebral microvessels and, therefore, is a possible explanation for the supersensitivity to NO observed in patients with migraine.

Nitric oxide pathway, Ca2+, and serotonin content in platelets from patients suffering from chronic daily headache

An alteration in serotonin concentration has been found in patients with chronic headache caused by abuse of analgesic substances as well as an up-regulation of 5HT2 platelet receptors, which has been correlated with chronicization of the headache. In a previous study we demonstrated an increase in L-arginine/nitric oxide (NO) pathway activity in platelets from patients affected by migraine with or without aura, particularly during attacks. In the present research we assessed the variations in platelet L-arginine/NO pathway and cyclic guanosine monophosphate (cGMP) levels in 32 patients affected by chronic daily headache (CDH) (8 M, 24 F, age range 34-50 years) both during and between attacks. In these same patients, the platelet aggregation to different collagen concentrations (0.3, 1, 3 micrograms/ml) was determined as well as the intracellular platelet calcium concentration using fluorescence polarization spectrometry. These parameters were compared with those of an age- and sex-matched control group (n = 25; n = 10, n = 15, age range 35-51 years). A reduction found in platelet aggregation response to each collagen concentration used (p < 0.001) was coupled with an increased NO and cGMP production (NO: p < 0.0001; cGMP: p < 0.001). This was accompanied by a significant increase in intracytosolic Ca2+ (p < 0.0001) concentration and a reduced platelet serotonin content compared to those in control individuals (p < 0.0002). Changes in the above platelet parameters were accentuated more in patients with analgesic abuse than in CDH patients with no drug abuse. These findings suggest the occurrence of an activation of cGMP-Ca2+ mediated events in CDH patients with analgesic abuse. This physiologic compensatory mechanism, which intervenes in overcoming the increase in cytosolic Ca2+ levels, is not as efficient at limiting serotonin depletion by platelet dense bodies. A similar depletion in the central serotoninergic pathway can be assumed in the same patients.