Nitric oxide metabolites, prostaglandins and trigeminal vasoactive peptides in internal jugular vein blood during spontaneous migraine attacks

Pharmacogenetics of migraine: genetic variants and their potential role in migraine therapy

Migraine is a paroxysmal neurological disorder affecting up to 6% of males and 18% of females in the general population, and has been demonstrated to have a strong, but complex, genetic component. Genetic investigation of migraine provides hope that new targets for medications and individual specific therapy will be developed. The identification of polymorphisms or genetic biomarkers for disease susceptibility and treatment should aid in providing a better understanding of migraine pathology and, consequently, more appropriate and efficient treatment for migraineurs. In this review, we will discuss results investigating genetic biomarkers for migraine and their potential role in future therapy planning.

Molecular mechanisms of migraine?

Migraine is a common debilitating neurological disease characterised by attacks of severe headache with or without preceding aura. Its aetiology remains elusive; however it is clear that an interplay of genetic and environmental components play an important role. Familial hemiplegic migraine (FHM) is a rare and severe variant of migraine with aura and follows an autosomal dominant pattern of inheritance. This disease is genetically heterogeneous,with three causative genes having been identified. This review uses insights garnered from FHM to try and shed light on possible migraine disease pathogenesis.

Dialysis headache

We describe the various side effects occurring in dialysis sessions and indicate measures for their prevention and/or treatment. Next, we analyze dialysis headache in terms of incidence, prevalence, criteria for its inclusion in the classification of the International Headache Society, and factors related to its triggering, ie, bradykinin and nitric oxide (NO), which have increased plasma levels during dialysis. This permits a critical analysis in comparison with NO donor headache in terms of the pathophysiologic mechanisms that mediate the triggering of both conditions. A similarity is particularly detected in terms of the role of NO as the last link in the chain of events that precedes the onset of headache, which is preceded by a latency period of 3 to 4 hours, much longer than the few seconds needed to inactivate NO. A hypothesis is raised to explain this phenomenon, opening new perspectives for the study of the pathophysiology of headaches, including primary headaches.

Episodic dural stimulation in awake rats: a model for recurrent headache

OBJECTIVES

To model, in rats, the development of chronic trigeminal nociceptive hypersensitivity seen in patients with recurrent headache.

BACKGROUND

Pathophysiology studies suggest that patients with recurrent migraine headache experience repeated bouts of dural nociceptor activation. In some patients, the severity and frequency of headache attacks increase over time. Patients with recurrent headache are hypersensitive to nitric oxide donors, such as glyceryl trinitrate (GTN). Current trigeminal pain models do not reflect the repeated episodic nature of dural nociceptor activation in patients with recurrent headache. Repeated nociceptor activation creates long-lasting changes in the periphery and brain due to activity-dependent neuronal plasticity. An animal model of repeated activation of dural nociceptors will facilitate the study of the physiological changes caused by repeated, episodic pain and the factors important for the transition of episodic to chronic migraine.

METHODS

We induced dural inflammation by infusing an inflammatory soup (IS) through a cannula on the dura in awake behaving rats. This was repeated 3 times per week for up to 4 weeks. Periorbital pressure sensory testing was used to monitor the change in trigeminal sensitivity. Rats were challenged with GTN to test the hypothesis that many dural stimulations are required to model the hypersensitivity of migraine patients. Quantitative trigeminal sensory testing and microdialysis in the trigeminal nucleus caudalis (TNC) were used to measure GTN hypersensitivity.

RESULTS

Multiple infusions of IS (>8), over weeks, induced a long-lasting decrease in periorbital pressure thresholds that lasted >3 weeks after the last infusion. In contrast, IS infusion in IS-naive rats and those that received 3 IS infusions produced only short-lasting decreases in periorbital pressure thresholds. Rats that received more than 8 IS infusions showed a marked increase in their neurochemical and behavioral responses to GTN. In these rats, GTN induced a decrease in periorbital von Frey thresholds that lasted >5 hours. In contrast, in rats that received only 3 IS infusions, GTN caused a threshold decrease for 1.5 hour. In vivo microdialysis in the TNC showed that GTN increased extracellular glutamate levels in rats with more than 8 IS infusions to 7.7 times the basal levels. In IS-naive rats and those that received only 3 IS infusions, the extracellular glutamate levels rose to only 1.7 and 1.9 times the basal level, respectively.

CONCLUSIONS

Repeated IS stimulation of the dura produces a chronic state of trigeminal hypersensitivity and potentiates the response to GTN. This hyperresponsiveness outlasts the last IS infusion and is the basis of our rat model of recurrent headache. This model can be used to study the changes in the brain and periphery induced by repeated trigeminovascular nociceptor activation and has the potential to elucidate the mechanisms for the transition of episodic to chronic headache.

Effects of autogenic training on nitroglycerin-induced headaches

OBJECTIVES

To investigate the prophylactic and acute effects of autogenic training (AT) during a nitroglycerin-induced migraine attack.

METHODS

Thirty female migraineurs (without aura) and 11 controls participated in the study. Of these, 11 migraineurs and 5 controls practiced AT regularly for at least 6 months prior to and during the sublingual nitroglycerin test. Headache intensity and characteristics were recorded with a standardized method. During the nitroglycerin challenge, blood was collected for plasma cortisol determination and blood pressure and pulse rate were recorded.

RESULTS

As a long-term preventive treatment, AT significantly decreased the mean headache frequency and intensity (P = .001) compared to the pretreatment period in the migraineurs who regularly practiced AT (n = 11). During the nitroglycerin challenge, AT successfully attenuated the nitroglycerin-induced acute decrease in blood pressure and pulse rate (P = .013; n = 16 AT subjects vs n = 25 non-AT subjects). However, it was not effective in preventing immediate headache (P = .71), did not decrease the frequency of acute migraine attacks (P = .79), and could not alleviate acute migraine pain (P = .78; n = 16 AT subjects vs n = 25 non-AT subjects). Plasma cortisol concentration significantly increased (P = .003) during the acute migraine attack (n = 22), and migraine intensity correlated with plasma cortisol elevations (P < .001; n = 41) and showed a tendency of negative correlation with morning plasma cortisol concentration (P = .08; n = 41). However, AT did not alter plasma cortisol responses (P = .99; n = 16 AT subjects vs n = 25 non-AT subjects).

CONCLUSION

(1) The long-term AT therapy proved to be a significantly effective preventive intervention in migraine sufferers. We hypothesized that this long-term effect of AT is based on modulation of the pain anticipation system, which is strongly correlated with function of the anterior cingulate cortex. (2) We demonstrated that AT could not alter the nitroglycerin-induced acute migraine attacks, which are directly related to the dysfunctional brainstem activation according to previous studies. (3) Our results suggested that there are multiple, complex relationships between cortisol responses and migraine pain, which are possibly mediated by the brain serotonergic system. (4) In addition, our results provide further evidence that nitroglycerin-induced vasodilatation is not directly connected to either immediate headache or delayed migraine attack.

Endothelial function in patients with migraine during the interictal period

OBJECTIVES

The aim of this study is to evaluate endothelial function in migraineurs subjects during the asymptomatic period.

BACKGROUND

Migraine has been proposed as a risk factor for cerebrovascular events. The underlying mechanisms that relate these 2 pathologies are unknown. Nitric oxide (NO) has been proposed as the final causative molecule of migraine. Increased NO metabolites concentrations have been reported in migraineurs subjects during acute migraine attacks, but there is no evidence indicating alterations in endothelial NO release during the symptom free period in theses subjects.

DESIGN AND METHODS

Fifty migraineurs subjects and 25 healthy subjects matched by gender and age were included. Every subject underwent a complete examination that included medical history, physical examination, resting electrocardiogram, forearm flow-mediated vasodilation (FMD), blood determinations of fasting nitrates and nitrites (NO(2) (-)+ NO(3) (-)), glucose, lipid profile, creatinine, C-reactive protein, and blood cell count.

RESULTS

No differences in FMD or NO(2) (-)+ NO(3) (-) were detected among groups. The only difference between migraineurs and control subjects was a higher mean blood pressure 92.1 (8.8) mmHg versus 86.7 (8.2) mmHg P= .01.

CONCLUSION

The endothelial function is not altered during the interictal period in migraineurs subjects.

Recurrent headache as the main symptom of acquired cerebral toxoplasmosis in nonhuman immunodeficiency virus-infected subjects with no lymphadenopathy: the parasite may be responsible for the neurogenic inflammation postulated as a cause of different types of headaches

Headache and/or migraine, a common problem in pediatrics and internal medicine, affect about 5% to 10% children and adolescents, and nearly 30% of middle-aged women. Headache is also one of the most common clinical manifestations of acquired Toxoplasma gondii infection of the central nervous system (CNS) in immunosuppressed subjects. We present 11 apparently nonhuman immunodeficiency virus-infected children aged 7 to 17 years (8 girls, 3 boys) and 1 adult woman with recurrent severe headaches in whom latent chronic CNS T. gondii infection not manifested by enlarged peripheral lymph nodes typical for toxoplasmosis, was found. In 7 patients, the mean serum IgG Toxoplasma antibodies concentration was 189 +/- 85 (SD) IU/mL (range 89 to 300 IU/mL), and in 5 other subjects, the indirect fluorescent antibody test titer ranged from 1:40 to 1:5120 IU/mL (n= <1:10 IU/mL). Some of the patients suffered also from atopic dermatitis (AD) and were exposed to cat and/or other pet allergens, associated with an increased IL-4 and decreased IFN-gamma production. These cytokine irregularities caused limited control of cerebral toxoplasmosis probably because IL-4 down-regulated both the production of IFN-gamma and its activity, and stimulated production of a low NO-producing population of monocytes, which allowed cysts rupture, increased parasite multiplication and finally reactivation of T. gondii infection. The immune studies performed in 4 subjects showed a decreased percentage of T lymphocytes, increased total number of lymphocytes B and serum IgM concentration, and impaired phagocytosis. In addition, few of them had also urinary tract diseases known to produce IL-6 that can mediate immunosuppressive functions, involving induction of the anti-inflammatory cytokine IL-10. These disturbances probably resulted from the host protective immune reactions associated with the chronic latent CNS T. gondii infection/inflammation. This is consistent with significantly lower enzyme indoleamine 2,3-dioxygenase (IDO) activity reported in atopic than in nonatopic individuals, and an important role that IDO and tryptophan degradation pathways plays in both, the host resistance to T. gondii infection and its reactivation. Analysis of literature information on the subjects with different types of headaches caused by foods, medications, and other substances, may suggest that their clinical symptoms and changes in laboratory data result at least in part from interference of these factors with dietary tryptophan biotransformation pathways. Several of these agents caused headache attacks through enhancing NO production via the conversion of arginine to citrulline and NO by the inducible nitric oxide synthase enzyme, which results in the high-output pathway of NO synthesis. This increased production of NO is, however, quickly down-regulated by NO itself because this biomolecule can directly inactivate NOS, may inhibit Ia expression on IFN-gamma-activated macrophages, which would limit antigen-presenting capability, and block T-cell proliferation, thus decreasing the antitoxoplasmatic activity. Moreover, NO inhibits IDO activity, thereby suppressing kynurenine formation, and at least one member of the kynurenine pathway, 3-hydroxyanthranilic acid, has been shown to inhibit NOS enzyme activity, the expression of NOS mRNA, and activation of the inflammatory transcription factor, nuclear factor-kB. In addition, the anti-inflammatory cytokines IL-4 and IL-10, TGF-beta, and a cytokine known as macrophage deactivating factor, have been shown to directly modulate NO production, sometimes expressing synergistic activity. On the other hand, IL-4 and TGF-beta can suppress IDO activity in some cells, for example human monocytes and fibroblasts, which is consistent with metabolic pathways controlled by IDO being a significant contributor to the proinflammatory system. Also, it seems that idiopathic intracranial hypertension, pseudotumor cerebri, and aseptic meningitis, induced by various factors, may result from their interference with IDO and inducible nitric oxide synthase activities, endogenous NO level, and cytokine irregularities which finally affect former T. gondii status 2mo in the brain. All these biochemical disturbances caused by the CNS T. gondii infection/inflammation may also be responsible for the relationship found between neurologic symptoms, such as headache, vertigo, and syncope observed in apparently immunocompetent children and adolescents, and physical and psychiatric symptoms in adulthood. We therefore believe that tests for T. gondii should be performed obligatorily in apparently immunocompetent patients with different types of headaches, even if they have no enlarged peripheral lymph nodes. This may help to avoid overlooking this treatable cause of the CNS disease, markedly reduce costs of hospitalization, diagnosis and treatment, and eventually prevent developing serious neurologic and psychiatric disorders.

Entzündliche Erkrankungen des ZNS sowie immunmodulatorische Therapie und ihr Einfluss auf primäre Kopfschmerzen

Headaches are a well known symptom in systemic or local inflammatory diseases such as pneumonia or meningitis. These headaches may mimic primary headaches and are thought to be generated by inflammatory mediators acting directly on nociceptors or indirectly - via facilitation of neurons. Apart from prostaglandin and nitric oxide also cytokines (TNF-alpha or interleukin-6) may play a role. In primary headaches such as migraine inflammatory mechanisms also have been acclaimed to contribute to pain generation. The recently observed increase of migraine attacks under immunmodulatory therapy in multiple sclerosis has focussed attention on primary headaches in states of altered immunity, for instance in autoimmune disorders like lupus erythematosus, rheumatoid arthritis, or in patients treated with immunosuppressants. This article describes the standard of knowledge and tries to shed light on possible mechanisms of pain generation in the respective conditions.

A role for brain cyclooxygenase-2 and prostaglandin-E2 in migraine: effects of nitroglycerin

Cyclooxygenase-2 (COX-2) may increase prostaglandin E(2) (PGE(2)) production in central nervous system (CNS) and contribute to the severity of pain responses in inflammatory pain. In this chapter, we sought to evaluate the possible role of COX-2 induction and prostaglandins (PGs) synthesis within neuronal areas proposed to be involved in migraine genesis in the animal model of migraine based on the administration of systemic nitroglycerin (NTG). Male Sprague-Dawley rats were injected with NTG (10mg/kg, i.p.) or vehicle and sacrificed 2 and 4h later. The hypothalamus and the lower brain stem were dissected out and utilized for the evaluation of COX-2 expression by means of Western blotting and for the determination of PGE(2) levels by means of ELISA immunoassay. COX-2 expression increased in the hypothalamus at 2h and in the lower brain stem at 4h. PGE(2) levels showed an opposite pattern of change with a decrease in PGE(2) levels at 2h in the hypothalamus and an increase at 4h in the lower brain stem. These data support the hypothesis that NTG administration is capable of activating the COX-2 pathway within cerebral areas. This activity may explain the pronociceptive effect of NTG described in animal and human models of pain. Most importantly, these findings point to mediators and areas that may be relevant for migraine pathogenesis and treatment.

Increased urinary excretion of nitric oxide metabolites in longitudinally monitored migraine patients

This study evaluated a relationship between nitric oxide (NO) and migraine attacks in order to gain insight into migraine pathomechanism. The study groups consisted of 12 migraineurs and eight controls. All subjects collected morning urine samples for 40 consecutive days. Urinary NO metabolites, nitrite/nitrate (NO(x)) levels were measured with the vanadium-based assay, whilst creatinine (Cr) and neopterin were determined with high-performance liquid chromatography. The mean urinary NO(x)/Cr ratio and number of NO(x) peaks was significantly greater in the migraine group compared with controls (P = 0.01 and P = 0.007, respectively). In the second approach, high NO(x) values were re-assessed in relation to raised neopterin, a marker of systemic infection or inflammation, and were excluded. The excretion of NO(x) persisted being pulsatile, and migraineurs had more peaks compared with controls (P = 0.01). In seven patients, NO(x) peaks coincided with headache days. This was more frequent than expected by random association in four patients (Monte-Carlo simulation; odds ratios: 2.16-7.77; no overlap of 95% CI). In four patients, NO(x) peaks preceded or followed headache days. Although there is a difference in the pattern of urinary NO(x) excretion between control and migraine populations, the variable temporal association of NO(x) peaks and headaches suggests a complex role of NO in this condition.

Increased plasma substance P and CGRP levels, and high ACE activity in migraineurs during headache-free periods

Substance P (SP), calcitonin gene-related peptide (CGRP), and angiotensin converting enzyme (ACE) may have roles in trigeminovascular nociceptive mechanisms. We investigated interictal levels of SP, CGRP, ACE activity, and their correlation, in a sample of migraineurs. Forty-one patients suffering from migraine with aura (MA), 54 without aura (MO), and 52 non-headache subjects (controls) participated in this study. Blood samples were collected from cubital veins. Plasma levels of SP and CGRP were measured by enzyme immunoassay. Plasma ACE activities were measured spectrophotometrically. SP levels in MA (6.6+/-3.7 pg/ml; mean+/-SD) and MO (6.6+/-3.2 pg/ml) were significantly higher than in controls (4.8+/-2.4 pg/ml) (P<0.01). CGRP levels in MA (18.8+/-8.8 pg/ml) and MO (19.1+/-9.4 pg/ml) were also significantly higher than in controls (13.4+/-4.4 pg/ml) (P<0.01). ACE activities in MA (34.6+/-19.0 U/l) were significantly higher than in MO (25.3+/-13.2 U/l) and controls (27.0+/-20.4 U/l) (P<0.05). There was a significant correlation between SP and CGRP levels (P<0.05). In MA, SP and CGRP showed a tendency toward positive correlation, which was not significant. There was a weak, but significant positive correlation between SP levels and ACE activities (P<0.01). However, a relationship between ACE activities and CGRP levels was not observed. The data suggest that SP, CGRP, and ACE are relevant to migraine pathophysiology, and that they may interact.

Calcitonin gene-related peptide enhances release of native brain-derived neurotrophic factor from trigeminal ganglion neurons

Activity-dependent plasticity in nociceptive pathways has been implicated in pathomechanisms of chronic pain syndromes. Calcitonin gene-related peptide (CGRP), which is expressed by trigeminal nociceptors, has recently been identified as a key player in the mechanism of migraine headaches. Here we show that CGRP is coexpressed with brain-derived neurotrophic factor (BDNF) in a large subset of adult rat trigeminal ganglion neurons in vivo. Using ELISA in situ, we show that CGRP (1-1000 nM) potently enhances BDNF release from cultured trigeminal neurons. The effect of CGRP is dose-dependent and abolished by pretreatment with CGRP receptor antagonist, CGRP(8-37). Intriguingly, CGRP-mediated BDNF release, unlike BDNF release evoked by physiological patterns of electrical stimulation, is independent of extracellular calcium. Depletion of intracellular calcium stores with thapsigargin blocks the CGRP-mediated BDNF release. Using transmission electron microscopy, our study also shows that BDNF-immunoreactivity is present in dense core vesicles of unmyelinated axons and axon terminals in the subnucleus caudalis of the spinal trigeminal nucleus, the primary central target of trigeminal nociceptors. Together, these results reveal a previously unknown role for CGRP in regulating BDNF availability, and point to BDNF as a candidate mediator of trigeminal nociceptive plasticity.

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.

Dipyridamole may induce migraine in patients with migraine without aura

Dipyridamole inhibits phosphodiesterase 5 (PDE5) and adenosine re-uptake. The most prominent side-effect is headache. We examined the migraine-generating effects of dipyridamole as well as the cerebral blood velocity response in a single-blind study, including 10 patients with migraine without aura and 10 healthy subjects. Dipyridamole 0.142 mg/kg per min was administered intravenously. Headache intensity was scored on a verbal rating scale along with pain characteristics and accompanying symptoms. Blood velocity in the middle cerebral artery (V(mca)), blood pressure and heart rate were recorded repeatedly. Headache was induced in all migraine patients and in eight of 10 healthy subjects (P = 0.47) with no significant difference in headache intensity (P = 0.53). However, five patients but only one healthy subject experienced the symptoms of migraine without aura, according to ICHD-2 criteria, within 12 h (P = 0.14). Four patients reported photophobia after dipyridamole compared with no healthy subjects (P = 0.087). V(mca) decreased (P < 0.001) during and after dipyridamole infusion with no difference between groups (P = 0.15) coinciding with initiation, but not cessation of immediate headache. Thus, dipyridamole induces symptoms of migraine and an initial decrease in V(mca) in migraine patients, but not significantly more than in healthy subjects. This relatively low frequency of migraine induction, compared with nitric oxide donors and sildenafil, is probably due to the less specific action of dipyridamole on the cGMP signalling pathway as well as a possible bidirectional effect of adenosine on migraine induction.

Effects of parecoxib on plasma protein extravasation and c-fos expression in the rat

OBJECTIVE

We aimed to investigate the effects of the cyclooxygenases-2 (COX-2) inhibitor parecoxib on meningeal plasma protein extravasation (PPE) and on c-fos expression in the nucleus trigeminalis caudalis in an animal model of trigeminovascular activation. Background.-Recent reports about the efficacy of COX-2 inhibitors in migraine treatment suggest the involvement of COX-2 in migraine pathophysiology. So far, studies on the role of COX-2 in animal models of migraine are lacking.

METHODS

Unilateral electrical stimulation of the trigeminal ganglion was performed in anesthetized male Sprague Dawley rats. We assessed PPE in the ipsilateral dura mater and expression of c-fos within the ipsilateral trigeminal nucleus caudalis (TNC) under control conditions and after pretreatment with parecoxib.

RESULTS

Parecoxib significantly attenuated PPE in the rat dura mater. The PPE ratio under control conditions (1.73 +/- 0.19 (mean +/- SD)) was reduced by 58.9 +/- 30% after pretreatment with 10 mg/kg parecoxib and by 78.1 +/- 23% after pretreatment with 50 mg/kg. c-fos experiments: Compared with vehicle, all doses of parecoxib (1 mg/kg, 10 mg/kg, 50 mg/kg) significantly reduced the number of c-fos positive cells in the ipsilateral TNC (P < .05). The number of c-fos positive cells in the ipsilateral TNC was 50 +/- 2.7 (mean +/- SEM) under control conditions and 9.1 +/- 0.6 after pretreatment with 50 mg/kg parecoxib.

CONCLUSION

Our study results suggest that COX-2 is involved in neurogenic inflammation of the rat dura mater. Moreover, the study points to a role of COX-2 inhibitors in trigeminal nociception at the second-order level.

Proinflammatory cytokines, adhesion molecules, and lymphocyte integrin expression in the internal jugular blood of migraine patients without aura assessed ictally

OBJECTIVE

The aim of the present research was to verify the levels of the soluble adhesion molecules sL- and sE-selectins, intercellular adhesion molecule (sICAM)-1, and vascular cell adhesion molecule-1 in serial samples of internal jugular venous blood taken from migraine patients without aura (MWoA) during attacks. The expression of leukocyte function antigen (LFA)-1 and very late activation antigen (VLA)-4 was also assessed on lymphocytes obtained from jugular venous blood. Levels of certain proinflammatory cytokines (tumor necrosis factor-alpha[TNF-alpha], interleukin-1beta[IL-1beta], IL-4, and IL-6) were also determined and correlated with those of adhesion molecules.

PATIENTS AND METHODS

Seven MWoA patients were admitted in the hospital during attacks and blood samples were taken immediately after catheter insertion, at 1, 2, and 4 hours after attack onset, and within 2 hours after its termination. The levels of adhesion molecules and cytokines were measured with ELISA method. The expression of LFA-1 and VLA-4 was assessed by flow cytometry.

RESULTS

A parallel transient increase of sICAM-1, TNF-alpha, and IL-6 was observed in the first 2 hours after attack onset compared with the time of catheter insertion (P < .0001, <.001, and <.003, respectively). The proportion of CD4+ and CD8+ T-cells expressing high levels of LFA-1 showed instead a progressive down-regulation with significantly lower percentages at 2 and 4 hours after attack onset (P < .01 and <.022, respectively). No variation in the percentage of VLA-4 expressing cells was observed at any time of the study.

CONCLUSIONS

The transient increase in sICAM-1 and TNF-alpha found in the internal jugular blood of MWoA patients assessed ictally can be induced by sensory neuropeptides released from activated trigeminal endings. The progressive decrease in sICAM-1 levels during attacks and the down-regulation of LFA-1 expression by lymphocytes could antagonize their transvascular migration, supporting the hypothesis of sterile inflammation in the dura mater during migraine attacks.

Migraine and Patent Foramen Ovale: A Residual Coincidence or a Pathophysiological Intrigue?

Migraine is one of the most common neurological disorders and one of the most frequent primary headaches. It imposes a significant burden on the affected individuals, society and health care system. As the etiology and pathophysiology of migraine are not well understood, treatment is largely symptomatic. Patent foramen ovale is a remnant of a fetal circulation and is highly prevalent in the general population. Its presence was linked to several disorders including migraine. The aim of this review was to search in the available data the answer to the question whether the link between migraine and patent foramen ovale is coincidental or whether they represent a pathophysiological entity.

Delayed upregulation of ATP P2X3 receptors of trigeminal sensory neurons by calcitonin gene-related peptide

Recent evidence indicates a key role for the neuropeptide calcitonin gene-related peptide (CGRP) in migraine pain, as demonstrated by the strong analgesic action of CGRP receptor antagonists, although the mechanisms of this effect remain unclear. Most trigeminal nociceptive neurons releasing CGRP also express ATP-activated purinergic P2X3 receptors to transduce pain. To understand whether the CGRP action involves P2X3 receptor modulation, the model of trigeminal nociceptive neurons in culture was used to examine the long-term action of this peptide. Although 79% of CGRP-binding neurons expressed P2X3 receptors, acute application of CGRP did not change P2X3 receptor function. Nevertheless, after 1 h of CGRP treatment, strong enhancement of the amplitude of P2X3 receptor currents was observed together with accelerated recovery from desensitization. Receptor upregulation persisted up to 10 h (despite CGRP washout), was accompanied by increased P2X3 gene transcription, and was fully prevented by the CGRP antagonist CGRP(8-37). Surface biotinylation showed CGRP augmented P2X3 receptor expression, consistent with confocal microscopy data indicating enhanced P2X3 immunoreactivity beneath the neuronal membrane. These results suggest that CGRP stimulated trafficking of P2X3 receptors to the cell-surface membrane. Using pharmacological tools, we demonstrated that this effect of CGRP was dependent on protein kinase A and PKC activation and was prevented by the trafficking inhibitor brefeldin A. Capsaicin-sensitive TRPV1 vanilloid receptors were not upregulated. The present data demonstrate a new form of selective, slow upregulation of nociceptive P2X3 receptors on trigeminal neurons by CGRP. This mechanism might contribute to pain sensitization and represents a model of neuronal plasticity in response to a migraine mediator.

Neuronal Signal Substances as Biomarkers of Migraine

Of the sensory nervous system associated signal substances it is only calcitonin generelated peptide (CGRP) that is reliably associated with the degree of pain in the acute attacks of primary headaches. The treatment with triptans alleviates both the pain and the associated CGRP release, putatively via a presynaptic effect on the sensory nerves. The studies of opoids and other sensory neuropeptides are inconsistent and require further analysis. Initial positive data on endothelin and its receptors have turned out negative. Nitric oxide mechanisms are still debated both in terms of initiation of attacks and for the treatment.

Phosphodiesterase 3 and 5 and cyclic nucleotide-gated ion channel expression in rat trigeminovascular system

Activation of the trigeminovascular pain signalling system appears involved in migraine pathophysiology. However, the molecular mechanisms are only partially known. Stimulation of cAMP and cGMP production as well as inhibition of their breakdown induce migraine-like headache. Additionally, migraine may be associated with mutations in ion channels. The aim of the present study was to describe the expression of phosphodiesterase 3 (PDE3) and 5 (PDE5) and cyclic nucleotide-gated ion channels (CNG) in cerebral arteries, meninges, and the trigeminal ganglion. mRNA for PDE and CNG was determined in the rat middle cerebral artery, basilar artery, trigeminal ganglion, and dura mater using real-time PCR. PDE and CNG proteins were identified using Western blot. For comparison, rat aorta and mesenteric artery were analysed. PDE3A, PDE3B, and PDE5A mRNA were detected in all tissues examined except for PDE3A mRNA in dura mater and the trigeminal ganglion. PDE5A and PDE3A protein expression was present in both cerebral and peripheral arteries, whereas PDE3B protein was present only in the cerebral arteries. The CNGA4 and B1 subunit mRNAs were detected in cerebral arteries and CNGA2 also in the mesenteric artery. CNGA2 and A3 proteins were found in cerebral arteries and dura and CNGA1, CNGA2 and CNGA3 in the trigeminal ganglion. In conclusion, PDE3A, PDE3B, PDE5A, and five CNG subunits were expressed in several components of the trigeminovascular system of the rat. This suggests that modulation of cAMP and cGMP levels by PDE and activation of CNG may play a role in trigeminovascular pain signalling leading to migraine headache.

No increase of calcitonin gene-related peptide in jugular blood during migraine

Increased calcitonin gene-related peptide (CGRP) in external jugular venous blood during migraine attack is one of the most cited findings in the headache literature. The finding has not been convincingly reproduced and is based on comparison with historic control subjects. The validity of this finding is important for the understanding of migraine. We therefore investigated the issue using an intrapatient comparison design and two different CGRP assays. We sampled blood from the external jugular and cubital vein during, as well as outside of, an attack of migraine without aura. We succeeded in 17 patients, whereas only cubital fossa blood could be sampled in an additional 4 patients. CGRP was measured with the same assay as most previous studies (assay I) and furthermore with a more sensitive and validated assay (assay II). For assay I, mean CGRP concentration in external jugular venous blood during attack was 17.18 pmol/L compared with 15.88 pmol/L outside of attack. Mean difference was 1.81 pmol/L (95% confidence interval [CI]: -2.88, 6.41; p = 0.44). In peripheral blood during attack, CGRP was 16.86 pmol/L compared with 17.57 pmol/L outside of attack. Mean difference was -0.79 pmol/L (95% CI: -4.64, 3.06; p = 0.69). For assay II, external jugular venous blood concentration of CGRP during attack was 32.59 pmol/L compared with 30.59 pmol/L outside of attack; mean difference was 2.00 pmol/L (standard error, 2.39; 95% CI: -3.07, 7.07; p = 0.416). In peripheral blood during attack, CGRP was 33.37 pmol/L compared with 31.84 pmol/L outside of attack; mean difference was 1.53 pmol/L (standard error, 1.90; 95% CI: -2.46, 5.51; p = 0.431). Thus, no difference between CGRP level in external jugular or cubital fossa blood during and outside of attack was found. No difference was found between external jugular and peripheral venous blood. Thus, previous findings of increased CGRP level in external jugular or cubital fossa venous blood could not be confirmed. Our finding strongly suggests that CGRP is not increased in jugular venous blood during migraine without aura. CGRP cannot be used as a biomarker to validate human or animal models of migraine.

The importance of cytokines, chemokines and nitric oxide in pathophysiology of migraine

The certain etiology migraine is unknown. The study was aimed at determining to the efficiency of cytokines, chemokines and nitric oxide (NO) to the pathophysiology of migraine. The levels of cytokines, chemokines and NO in serum of 25 patients with migraine during attacks and attack-free periods and 25 healthy controls were investigated. The levels of cytokines and chemokines were determined by enzyme-linked immunosorbent assay. NO concentrations were determined by a nitrate/nitrite colorimetric assay kit. In attack groups, IL-10 levels were found higher than in attack-free groups and healthy controls (p<0.05). IL-6 levels in migraine patients were significantly higher than in healthy controls. The levels of RANTES were high in attacks groups. There was an increase NO concentrations in migraine attacks. The study's results reflect that the etiology of migraine is multifactorial and probably related to immunological changes.

Activation of the Transcription Factor NF-κB in the Nucleus Trigeminalis Caudalis in an Animal Model of Migraine

The infusion of nitroglycerin (NTG) induces an inflammatory state in perivascular meningeal tissues of rat via the activation, inter alia, of nuclear factor kappa B (NF-kappaB). This phenomenon has been related to the mechanisms involved in the pathophysiology of migraine, a common neurovascular disorder. In the present study, we sought to elucidate whether NF-kappaB activation might have a role in the determinism of migraine attacks also at the neuronal level. Therefore, we investigated the transcriptional activity of NF-kappaB in the brainstem of rats systemically injected with NTG and killed 4h later. Activation of NF-kappaB in brain areas was detected by means of both the immunohistochemical technique and the Western blot analysis. A significant increase of nuclear immunostaining of p65, an indicator of NF-kappaB activation, was detected in lamina I and II of nucleus trigeminalis caudalis in rats injected with NTG when compared with the control group. Western blot analysis confirmed the activation of the NF-kappaB pathway showing an increase in the optical density of p65 in nuclear extracts of lower brainstem of rats injected with the nitric oxide (NO) donor. The present study contributes to expand on our understanding of the complex mechanisms by which NTG may trigger migraine-like headaches in migraineurs. Furthermore, these findings pave the way to new bio-molecular and pharmacological avenues for the development of innovative migraine therapies.

Reproducibility of forearm vasodilator response to intra-arterial infusion of calcitonin gene-related peptide assessed by venous occlusion plethysmography

AIMS

To assess the reproducibility of the forearm blood flow (FBF) response to intra-arterial infusion of calcitonin-gene related peptide (CGRP), measured by venous occlusion plethysmography. In addition, to compare different ways of expressing the FBF response and perform sample size calculations.

METHODS

On two separate visits, CGRP (10 ng min(-1) dl(-1) forearm) was infused for 45 min into the brachial artery of six healthy subjects. Reproducibility was assessed by calculating mean difference, repeatability coefficient, within-subject coefficient of variation (WCV) and intraclass correlation coefficient.

RESULTS

CGRP increased FBF from 2.8 +/- 0.4 and 3.2 +/- 0.7 (at baseline) to 15.4 +/- 1.4 and 15.2 +/- 1.5 ml min(-1) dl(-1) forearm (at 45 min) on visits 1 and 2, respectively (P < 0.0001 for both visits). Mean difference in FBF at 45 min between both visits was 0.3 ml min(-1) dl(-1) forearm (repeatability coefficient: 4.1 ml min(-1) dl(-1) forearm). This FBF response appeared to be more reproducible when expressed as absolute FBF in the infused arm (WCV 11%) compared with absolute FBF-ratio between both arms (WCV 37%), percentage change from baseline in FBF in the infused arm (WCV 29%) and percentage change from baseline in FBF-ratio (WCV 40%). When expressed as absolute FBF, a sample size of five (95% confidence interval: 2-12) subjects gives 90% power at a type I error probability of 0.05 to detect a 25% shift in FBF response.

CONCLUSIONS

Intra-arterial infusion of CGRP results in a forearm vasodilator response which is reproducible between days. This response is most reproducible when expressed as absolute FBF. The presented methodology provides a suitable pharmacodynamic model to assess the in vivo activity of CGRP-receptor antagonists in a small number of subjects.

Chemokine levels in the jugular venous blood of migraine without aura patients during attacks

OBJECTIVE

To investigate changes in the levels of calcitonin gene-related peptide and its intracellular messenger cyclic adenosine monophosphate in serial samples of internal jugular blood taken from migraine patients without aura assessed during attacks, and to assess their relationship with the levels of IL-8, MCP-1, and RANTES in the same samples.

BACKGROUND

Calcitonin gene-related peptide, the marker of trigeminovascular activation, is released in both the internal and external jugular venous blood of migraine patients during attacks. Experimental evidence demonstrated that when released from C-type sensory neurons in inflammatory pain models, it differentially induced expression of neutrophil chemotactic chemokine IL-8, but not monocyte chemotactic chemokine MCP-1 or lymphocyte chemotactic chemokine RANTES. These chemokines were never investigated in migraine.

DESIGN/METHODS

Eight migraine without aura patients were admitted to the hospital during the attacks. Internal jugular venous blood samples were taken immediately after catheter insertion, at the 1st, 2nd, and 4th hours after attack onset, and within 2 hours from its cessation. The levels of the sensory neuropeptide calcitonin gene-related peptide and the messenger cyclic adenosine monophosphate were measured by RIA method, and those of IL-8, MCP-1, and RANTES were measured by ELISA method.

RESULTS

Higher calcitonin gene-related peptide levels were found in the internal jugular venous blood of migraine without aura patients compared with the time of catheter insertion (ANOVA: P<.0001) with a peak at the first hour (52.6+/-9.2 ng/mL). A transient increase in IL-8 was observed at the 2nd and 4th hours (P<.01 and P<.002, respectively), whereas no changes in the levels of MCP-1 and RANTES were found at any time of the study. The increase in IL-8 was accompanied by a parallel increase in cyclic adenosine monophosphate.

CONCLUSIONS

The present study confirms previous findings of an increase in calcitonin gene-related peptide in internal jugular venous blood of migraine without aura patients during attacks. The transient increase in the levels of IL-8 concurs with the results of recent experimental research showing a calcitonin gene-related peptide-induced activation of IL-8 gene expression, but not RANTES and MCP-1, via the transcriptional factor AP-2, which mediates transduction in response to cyclic adenosine monophosphate. Although IL-8 is transiently increased during migraine attacks, an accumulation of leukocytes secondary to neurogenic inflammation is unlikely, as it is for other inflammatory events, because they are self limiting. Other events, including nitric oxide production, may contribute to counteract meningeal transvascular leukocyte migration during migraine attacks, as suggested by the model of sterile inflammation.

The role of CGRP and nicotinic receptors in centrally evoked facial blood flow changes

The release of CGRP in humans is associated with the occurrence of migraine headaches. The vasoactive neuropeptide is released by afferent neurones originating in the peripherally located trigeminal ganglion supplying the dura mater. The role of CGRP in migraine is further supported by recently released data showing that the CGRP-antagonist BIBN4096BS is clinically effective for the treatment of migraine headaches. Yet, the trigger for CGRP release during migraine attacks is not identified. It is suggested that the peripheral CGRP release during a migraine attack might be either triggered by direct activation of afferent dural neurones, or, by indirect activation via the central nervous system. Recently, we were able to show that the CGRP-antagonist BIBN4096BS is able to inhibit vasodilation induced by trigeminal ganglion stimulation. Now, we extend our studies to the investigation of facial blood flow changes induced by electrical stimulation of the brainstem trigeminal nucleus caudalis (TNC). Here, we show that stimulation of the TNC leads to a pronounced increase of facial blood flow. The nicotinic antagonist Hexamethonium reduced the evoked flow by approximately 50% (30 mg/kg), while the muscarinic antagonist Atropin did not influence the stimulation evoked blood flow. Application of BIBN4096BS (0.3 mg/kg, i.v.) diminished the evoked flow almost completely. Therefore, we conclude that CGRP represents the key player in TNC-induced facial vasodilation, while activation of nicotinic receptors modulates centrally induced peripheral neurogenic vasodilation.

Increased frequency of migraine among women with endometriosis

BACKGROUND

Our aim is to assess the prevalence and characteristics of headache in patients with endometriosis compared with women without this disease.

METHODS

One hundred and thirty-three women with histologically proven endometriosis and 166 controls were interviewed by a neurologist experienced in headache diagnosis; the headache disorders were classified according to the 1988 International Headache Society criteria.

RESULTS

The prevalence of migraine was significantly higher among women with endometriosis [n = 51, 38.3%; 95% confidence interval (CI) 30.1-47.2%] than in controls (n = 25, 15.1%; 95% CI 10.0-21.4%) (P < 0.001). Migraine with aura was observed in 18 women with endometriosis (13.5%) and in two controls (1.2%; P < 0.001). The age at migraine onset was significantly lower in women with endometriosis than in controls (16.4 versus 21.9 years; P = 0.001). No significant difference was observed in pain intensity and attack frequency between the two groups; a trend for women with endometriosis to have longer unmedicated attacks was observed. No significant correlation was observed between attack frequency, unmedicated headache duration, migraine intensity and the severity of endometriosis.

CONCLUSION

Migraine is more frequent in women with endometriosis than in controls, although its presence and characteristics are not related to the severity of endometriosis.

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.

Platelet-activating factor (PAF) in internal jugular venous blood of migraine without aura patients assessed during migraine attacks

The aim of the study was to verify the production of PAF and the activity of PAF acetyl-hydrolase (PAF-AH), the enzyme involved in the catabolism of this phospholipid mediator, in migraine attacks. Their levels were determined during migraine crises in serial samples of internal jugular venous blood taken from five migraine patients without aura, who were admitted to the hospital during the crises. Internal jugular venous blood samples were taken immediately after catheter insertion at 1, 2, and 4 h after attack onset, and within 2 h from its cessation. PAF was purified by high-performance liquid chromatography (HPLC) and determined by radioimmunoassay method. The enzymatic activity of PAF-AH was measured by reverse-phase HPLC, based on the derivatization with 7-diethylaminocoumarin-3-carbonylazide. In the internal jugular venous blood of migraine patients without aura (MO), an increase was observed in PAF levels, which was already evident at the time of catheter insertion (885.6 +/- 82.8) and at the first hour (868.4 +/- 65.24) (ANOVA: P < 0.0001). PAF levels remained elevated through the second (746.8 +/- 82.95), fourth (700.6 +/- 34.93) and sixth hours (644.4 +/- 42.85), and then decreased at the end of the attack, reaching levels significantly lower than those measured at the time of catheter insertion (565.5 +/- 38.34). The activity of PAF-AH showed an opposite trend with higher values at the first hour and significantly lower values at the second and fourth hours from the beginning of the migraine attack (ANOVA: P < 0.02). The increased production of PAF may account for persistent platelet activation during migraine crises, even in the presence of an increased production of nitric oxide (NO) end-products which, on the other hand, should instead intervene in counteracting and limiting platelet activation. Potential sources of PAF production are the endothelial cells from cerebral vessels, stimulated by trigeminal neuropeptides, platelets themselves, and mast cells, as suggested by the neurogenic inflammation model.

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.

Cluster headache

Cluster headache is a relatively rare episodic headache disorder.Although traditionally it is believed to be a male-related disorder,the sex ratios are changing toward a more even balance. The disorder is characterized by bouts of daily headaches with pain-free remissions for extended times. Though attacks are brief, they are severe and typically are associated with autonomic symptoms. Medical therapies are the mainstay of treatment, with the goal being prevention of headaches in a cycle. Acute therapies, although effective, may be limited in usefulness because of attack frequency. Intractable cases may benefit from histamine desensitization and surgical treatments.

Biphasic response to nitric oxide of spinal trigeminal neurons with meningeal input in rat--possible implications for the pathophysiology of headaches

Nitric oxide (NO) is suggested to play a causative role in the pathogenesis of primary headaches. Infusion of NO donors can trigger headache attacks, and products of NO metabolism are found to be increased in the cranial circulation in patients suffering from such headaches. To examine if NO is involved in mediating and maintaining spinal trigeminal neuronal activity, an animal model of meningeal nociception was used. In barbiturate-anesthetized rats, a cranial window was made to expose the parietal dura mater. An access to the medullary brain stem allowed extracellular action potentials to be recorded from neurons in the spinal trigeminal nucleus that received afferent input from the exposed dura. Slow intravenous infusion of the NO donor, sodium nitroprusside (SNP, 50 microg/kg), transiently increased spontaneous activity in a subset of neurons and, with a latency of 50 min, caused a progressive increase in impulse activity across the entire sample of neurons. A similar pattern of delayed activation was seen after topical application of the same dose of SNP onto the exposed medulla. Slow injection of the nonspecific inhibitor of NO synthase, N(omega)-nitro-l-arginine methyl ester (20 mg/kg), reduced the spontaneous activity in all neurons within 15 min. The results suggest that NO can induce delayed, slowly developing activation of central trigeminal neurons and that endogenous release of NO may contribute to the ongoing activity of these neurons. The delayed changes in neuronal activity may include gene expression of pro-nociceptive mediators. These mechanisms may be relevant for the pathogenesis of chronic headaches.

NO-induced migraine attack: strong increase in plasma calcitonin gene-related peptide (CGRP) concentration and negative correlation with platelet serotonin release

The aim of the present study was to investigate changes in the plasma calcitonin gene-related peptide (CGRP) concentration and platelet serotonin (5-hydroxytriptamine, 5-HT) content during the immediate headache and the delayed genuine migraine attack provoked by nitroglycerin. Fifteen female migraineurs (without aura) and eight controls participated in the study. Sublingual nitroglycerin (0.5 mg) was administered. Blood was collected from the antecubital vein four times: 60 min before and after the nitroglycerin application, and 60 and 120 min after the beginning of the migraine attack (mean 344 and 404 min; 12 subjects). In those subjects who had no migraine attack (11 subjects) a similar time schedule was used. Plasma CGRP concentration increased significantly (P<0.01) during the migraine attack and returned to baseline after the cessation of the migraine. In addition, both change and peak, showed significant positive correlations with migraine headache intensity (P<0.001). However, plasma CGRP concentrations failed to change during immediate headache and in the subjects with no migraine attack. Basal CGRP concentration was significantly higher and platelet 5-HT content tended to be lower in subjects who experienced a migraine attack. Platelet serotonin content decreased significantly (P<0.01) after nitroglycerin in subjects with no migraine attack but no consistent change was observed in patients with migraine attack. In conclusion, the fact that plasma CGRP concentration correlates with the timing and severity of a migraine headache suggests a direct relationship between CGRP and migraine. In contrast, serotonin release from platelets does not provoke migraine, it may even counteract the headache and the concomitant CGRP release in this model.

EP4 prostanoid receptor-mediated vasodilatation of human middle cerebral arteries

1. Dilatation of the cerebral vasculature is recognised to be involved in the pathophysiology of migraine. Furthermore, elevated levels of prostaglandin E(2) (PGE(2)) occur in the blood, plasma and saliva of migraineurs during an attack, suggestive of a contributory role. In the present study, we have characterised the prostanoid receptors involved in the relaxation and contraction of human middle cerebral arteries in vitro. 2. In the presence of indomethacin (3 microm) and the TP receptor antagonist GR32191 (1 microM), PGE(2) was found to relax phenylephrine precontracted cerebral arterial rings in a concentration-dependent manner (mean pEC(50) 8.0+/-0.1, n=5). 3. Establishment of a rank order of potency using the EP(4)>EP(2) agonist 11-deoxy PGE(1), and the EP(2)>EP(4) agonist PGE(1)-OH (mean pEC(50) of 7.6+/-0.1 (n=6) and 6.4+/-0.1 (n=4), respectively), suggested the presence of functional EP(4) receptors. Furthermore, the selective EP(2) receptor agonist butaprost at concentrations <1 microM failed to relax the tissues. 4. Blockade of EP(4) receptors with the EP(4) receptor antagonists AH23848 and EP(4)A caused significant rightward displacements in PGE(2) concentration-response curves, exhibiting pA(2) and pK(B) values of 5.7+/-0.1, n=3, and 8.4, n=3, respectively. 5. The IP receptor agonists iloprost and cicaprost relaxed phenylephrine precontracted cerebral arterial rings (mean pEC(50) values 8.3+/-0.1 (n=4) and 8.1+/-0.1 (n=9), respectively). In contrast, the DP and FP receptor agonists PGD(2) and PGF(2 alpha) failed to cause appreciable relaxation or contraction at concentrations of up to 30 microm. In the absence of phenylephrine contraction and GR32191, the TP receptor agonist U46619 caused concentration-dependent contraction of cerebral artery (mean pEC(50) 7.4+/-0.3, n=3). 6. These data demonstrate the presence of prostanoid EP(4) receptors mediating PGE(2) vasodilatation of human middle cerebral artery. IP receptors mediating relaxation and TP receptors mediating contraction were also functionally demonstrated.

5-HT(1B/1D) serotonin receptor agonist attenuates nitroglycerin-evoked nitric oxide synthase expression in trigeminal pathway

This study was conducted to investigate the effect of 5-HT(1B/1D) receptor activation on nitroglycerin (NTG)-induced cerebral hyperaemia and neuronal nitric oxide synthase (nNOS) expression in trigeminovascular neurones. NTG (10 mg/kg) was infused intravenously to adult male Wistar rats with or without pretreatment with 5-HT(1B/1D) receptor agonist, sumatriptan (0.4 mg/kg, intravenously). Cortical blood flow and expression of nNOS enzyme in trigeminal ganglia, trigeminal nucleus caudalis and perivascular nerve fibre surrounding superior sagittal sinus were measured. The results showed that pretreatment with sumatriptan could significantly shorten the period of NTG-induced cerebral hyperaemia without compromising the magnitude of hyperaemic peak. Sumatriptan pretreatment also attenuated the NTG-evoked expression of nNOS in all studied areas. Based on these findings, we suggest that 5-HT(1B/1D) receptor has an important role in stabilizing the trigeminovascular system by attenuating the expression of nNOS enzyme, hence reducing nitric oxide production.

Prostaglandin E2 injected into the posterior hypothalamus has no effect on trigeminal nociception in the rat

Craniovascular prostaglandin E2 (PGE2) release is elevated in the headache phase of migraine and in experimental models of headache. PGE2 synthesised in the brain may be involved in modulating trigeminal nociception. We examined whether PGE2 injected into the posterior hypothalamus could modulate trigeminovascular nociception. In seven rats, electrophysiological recordings were made from trigeminal nucleus caudalis neurons responsive to noxious middle meningeal artery stimulation and inhibited by bicuculline activation of the posterior hypothalamus. Microinjection into the posterior hypothalamus of a non-pyrogenic dose of PGE2 (2.5 microg/ml) produced no effect on nociceptive trigeminal nucleus caudalis neurons compared with saline injection (P=0.29). The mean response to PGE2 injection was 97% of baseline. We conclude that PGE2 in the posterior hypothalamus is unlikely to play a significant role in modulating trigeminal nociception.

Prostaglandin E2 is increased in amyotrophic lateral sclerosis patients

OBJECTIVES

Oxidative stress and glutamate-mediated excitotoxicity may play an important role in the etiopathogenesis of amyotrophic lateral sclerosis (ALS). Prostaglandin E2 (PGE2) activity can be associated with motor neuron death by inducing free radical formation and glutamate release from astrocytes. The aim of this study was to determine PGE2 concentration in the serum and cerebrospinal fluid (CSF) of ALS patients.

MATERIAL AND METHODS

PGE2 concentration was measured by the enzyme-linked immunosorbent method in the serum and CSF from ALS and control group patients.

RESULTS

Serum and CSF PGE2 concentration was significantly higher in the whole group of ALS patients compared with the control group patients (P < 0.05). There was no relationship between PGE2 concentration and clinical parameters of the disease, such as clinical state, type of ALS onset, and duration of the disease (P > 0.05). A significant correlation between CSF PGE2 concentration and age of control group patients was found (P < 0.05).

CONCLUSIONS

A significant increase in serum and CSF PGE2 concentration, in ALS patients observed in this study, indicates that PGE2 may play a role in neurodegeneration of ALS through oxidative damage of neurons and glutamate-mediated excitotoxicity. It suggests that inhibition of PGE2 synthesis could prevent motor neuron death. However, serum and CSF PGE2 cannot be a marker of the type of ALS onset, clinical state of patients, or the duration of the disease.

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.

Characterization of bradykinin-induced prostaglandin E2 release from cultured rat trigeminal ganglion neurones

Bradykinin and prostaglandins are both local mediators strongly implicated in pain and inflammation. Here, we have investigated the effects of bradykinin on the release of prostaglandin E(2) from cultured neurones derived from adult rat trigeminal ganglia. Bradykinin was a potent inducer of prostaglandin E(2) release, an effect that was likely mediated by bradykinin B(2) receptors, as the bradykinin-induced prostaglandin E(2) release was attenuated by the bradykinin B(2) receptor-selective antagonist, arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl)-L-alanyl-L-seryl-D-1,2,3,4-tetrahydro-3-isoquinolinecarbonyl-L-(2 alpha, 3 beta, 7a beta)-octahydro-1H-indole-2-carbonyl-L-arginine (HOE 140), but not by the bradykinin B(1) receptor-selective antagonist, des-Arg(9),[Leu(8)]-bradykinin. Furthermore, bradykinin-induced prostaglandin E(2) release was inhibited following treatment with the phospholipase A(2) inhibitor, arachidonyltrifluoromethyl ketone (AACOCF(3)), the nonselective cyclooxygenase inhibitor, piroxicam, the mitogen-activated protein kinase kinase-1 (MEK1) inhibitor, 2'-amino-3'-methoxyflavone (PD98059), and the protein kinase C inhibitor, bisindolylmaleimide XI (Ro320432). Taken together, these data suggest that bradykinin, acting via bradykinin B(2) receptors, induces prostaglandin E(2) release from trigeminal neurones through the protein kinase C and mitogen-activated protein kinase-dependent activation of phospholipase A(2) and consequent stimulation of cyclooxygenases.

CGRP-mediated cardiovascular effect of nitroglycerin

Organic nitrates, including nitroglycerin, produce vascular relaxation by releasing nitric oxide in vascular tissues near the plasma member of smooth muscle cells of veins and arteries. Calcitonin gene-related peptide (CGRP), a major transmitter in capsaicin-sensitive sensory nerves, is widely distributed in cardiovascular tissues and the release of CGRP is regulated by multiple autacoids including nitric oxide (NO). CGRP exerts complex cardiovascular effects including potent vasorelaxation and protective effects on myocytes and endothelial cells. Nitroglycerin activates sensory nerves fibres to release CGRP by generating NO and increasing cGMP level, and that the cardiovascular effects of nitroglycerin are partly mediated by endogenous CGRP.

Urinary nitric oxide metabolites and lipid peroxidation by-products in migraine

Enhanced endothelium nitric oxide (NO) and superoxide anion release may cause migraine through related cerebral blood flow changes. Thirty subjects suffering from migraine with and without aura and 20 healthy controls were investigated. Urine samples collected for 24 h during and after the migraine attack, and during the headache-free period, were assayed for urinary NO stable metabolites (NOx) and thiobarbituric acid reactive substances (TBARS). During the headache-free period urinary NOx and TBARS levels were higher in migraine sufferers than in controls (NOx 0.77 +/- 0.14 vs. 0.28 +/- 0.15 mmol/mmol creatinine, P < 0.05; TBARS 0.40 +/- 0.19 vs. 0.26 +/- 0.13 micro mol/mol creatinine, P < 0.05). Also, NOx excretion was higher during the headache-free period than during or after the migraine attack (P < 0.05). Urinary TBARS were increased during the attack with respect to the headache-free period (P < 0.05). No differences were observed in the same parameters between sufferers of migraine with and without aura. Urinary NOx and TBARS might be promising as markers of their systemic levels to evaluate the increased vulnerability to oxidative stress in migraine sufferers.

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.

2002 Wolff Award. 5 -HT2A receptor activation and nitric oxide synthesis: a possible mechanism determining migraine attacks

OBJECTIVE

To determine the effect of the 5-HT2A receptor in control of spinal nociception, cerebral circulation, and nitric oxide synthase (nNOS) expression in trigeminovascular neurons.

BACKGROUND

The plasticity of the 5-HT2A receptor is a possible factor determining the course of migraine. Up-regulation of this receptor has been demonstrated to correlate with the increasing frequency of migraine attacks and may underlie the development of chronic daily headache.

METHODS

Adult male Wistar rats were divided into groups receiving the 5-HT2A agonist, 1,2,5-dimethoxy-4-iodophenyl-2-aminopropane (DOI), nitroglycerin, or normal saline. The tail flick test and chemical nociception-evoked Fos-expression in dorsal horn neurons were used as indicators of nociception. Regional cerebral blood flow was monitored using laser Doppler flowmetry. Expression of Fos and nNOS was studied using immunohistochemical method.

RESULTS

Administration of DOI led to the shortening of tail flick latency (1.3 +/- 0.2 and 7.2 +/- 0.6 seconds for DOI-treated and control groups, respectively). The number of Fos-immunoreactive neurons was also greater in the DOI-treated group compared with the control group. DOI also produced long-lasting cerebral hyperemia (123% of baseline value) associated with the enlargement of perivascular nNOS-immunoreactive nerve fibers and increased nNOS-immunoreactive neurons in trigeminal ganglia and trigeminal nucleus caudalis. These findings resembled those observed in the rats exposed to nitroglycerin.

CONCLUSION

Our results suggest that activation of the 5-HT2A receptor leads to an enhancement of NO production in trigeminovascular pathway. NO may trigger migraine attacks by inducing cerebral vasodilation and sensitizing the perivascular nociceptors and central nociceptive neurons in trigeminovascular system. Up-regulation of this pronociceptive receptor can increase headache attacks and contributes to the development of chronic daily headache.