Differential distribution of 5HT1D- and 5HT1B-immunoreactivity within the human trigemino-cerebrovascular system: implications for the discovery of new antimigraine drugs

Exploring the Tryptophan Metabolic Pathways in Migraine-Related Mechanisms

Migraine is a complex neurovascular disorder, which causes intense socioeconomic problems worldwide. The pathophysiology of disease is enigmatic; accordingly, therapy is not sufficient. In recent years, migraine research focused on tryptophan, which is metabolized via two main pathways, the serotonin and kynurenine pathways, both of which produce neuroactive molecules that influence pain processing and stress response by disturbing neural and brain hypersensitivity and by interacting with molecules that control vascular and inflammatory actions. Serotonin has a role in trigeminal pain processing, and melatonin, which is another product of this pathway, also has a role in these processes. One of the end products of the kynurenine pathway is kynurenic acid (KYNA), which can decrease the overexpression of migraine-related neuropeptides in experimental conditions. However, the ability of KYNA to cross the blood-brain barrier is minimal, necessitating the development of synthetic analogs with potentially better pharmacokinetic properties to exploit its therapeutic potential. This review summarizes the main translational and clinical findings on tryptophan metabolism and certain neuropeptides, as well as therapeutic options that may be useful in the prevention and treatment of migraine.

Sumatriptan prevents central sensitisation specifically in the trigeminal dermatome in humans

BACKGROUND

The exact mechanism and site of action of triptans in aborting migraine attacks remain under debate. We hypothesized that the clinical efficacy of triptans lies in aborting central sensitization and focused on the question of why triptans are headache-specific, i.e. highly effective in migraine and cluster headache and ineffective in extracephalic pain.

METHODS

Forty healthy participants were enrolled in this double-blinded, randomized, placebo-controlled study. The effect of sumatriptan (n=20) vs placebo (n=20) was investigated in a cephalic (V1) vs an extracephalic dermatome (forearm) using a topical capsaicin sensitization model. Capsaicin-induced primary and secondary hyperalgesia were evaluated using quantitative sensory testing.

RESULTS

After capsaicin application, primary hyperalgesia developed in both sumatriptan and placebo groups in both dermatomes. However, sumatriptan exclusively prevented secondary hyperalgesia in the V1 dermatome but not on the forearm. Placebo exerted no effects on secondary hyperalgesia in both trigeminal and extracephalic dermatomes. Additionally, sumatriptan reduced the flare size exclusively in the V1 dermatome.

CONCLUSIONS

Our data suggest that sumatriptan reduces central sensitization (secondary hyperalgesia) without modulating peripheral sensitization (primary hyperalgesia) in a human pain model of capsaicin-induced sensitization. Moreover, despite a systemic administration of sumatriptan, the modulatory effects are trigeminal-specific, echoing the clinical effect of triptans in aborting headaches, but not extracephalic pain.

Recent advances in targeting calcitonin gene-related peptide for the treatment of menstrual migraine: A narrative review

Menstrual migraine (MM) has a longer duration and higher drug resistance than non-perimenstrual migraine. Calcitonin gene-related peptide (CGRP) and CGRP receptors are expressed in the peripheral and central nervous systems throughout the trigeminovascular system. The CGRP/CGRP receptor axis plays an important role in sensory physiology and pharmacology. CGRP receptor antagonists and anti-CGRP monoclonal antibodies (mAbs) have shown consistent efficacy and tolerability in the prevention of chronic or episodic migraine and are now approved for clinical use. However, few studies have reported the use of these drugs in MM, and no specific treatment for MM has been approved. This review aimed to shed light on the recent advances in targeting calcitonin gene-related peptides for the treatment of menstrual migraines in PubMed. In this review, we first discuss the axis of the CGRP/CGRP receptor. We then discuss the role of CGRP receptor antagonists and anti-CGRP mAbs in MM treatment. Finally, we discuss the role of the combination of anti-CGRP mAbs and CGRP receptor antagonists in migraine treatment and the drugs that inhibit CGRP release. Altogether, the anti-CGRP mAbs or CGRP receptor antagonists showed good efficacy and safety in the treatment of MM.

Using the Intranasal Route to Administer Drugs to Treat Neurological and Psychiatric Illnesses: Rationale, Successes, and Future Needs

While the intranasal administration of drugs to the brain has been gaining both research attention and regulatory success over the past several years, key fundamental and translational challenges remain to fully leveraging the promise of this drug delivery pathway for improving the treatment of various neurological and psychiatric illnesses. In response, this review highlights the current state of understanding of the nose-to-brain drug delivery pathway and how both biological and clinical barriers to drug transport using the pathway can been addressed, as illustrated by demonstrations of how currently approved intranasal sprays leverage these pathways to enable the design of successful therapies. Moving forward, aiming to better exploit the understanding of this fundamental pathway, we also outline the development of nanoparticle systems that show improvement in delivering approved drugs to the brain and how engineered nanoparticle formulations could aid in breakthroughs in terms of delivering emerging drugs and therapeutics while avoiding systemic adverse effects.

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.

Migraine Pathophysiology

Migraine is the leading cause of years lost due to disability in individuals aged 15 to 49 years. Much has changed over the last three decades about our understanding of this complex neurological disorder. Various phases of migraine have been characterized and are the focus of this review. The premonitory phase involves bothersome symptoms experienced hours to days before migraine pain. Behavioral changes and functional neuroimaging studies point toward hypothalamic involvement during the premonitory and other migraine phases. Migraine aura is a disruptive, reversible neurological phenomenon that affects up to one-third of all migraineurs, and can overlap with the headache phase. The mechanism responsible for this phase is thought to be cortical spreading depolarization through the cortex. This process leads to temporary disruptions in ion homeostasis and the ensuing neuronal dysfunction. The headache phase involves activation of the trigeminocervical complex. Neuropeptides are implicated in trigeminal activation, and calcitonin gene-related peptide in particular has become a promising target of therapeutic intervention for migraine. The final phase of migraine is the postdrome, the period of time from the resolution of headache symptoms until return to baseline following a migraine. People often report neuropsychiatric, sensory, gastrointestinal, and general symptoms during this time, which can limit activity. Elucidating the neuroanatomical, chemical, and neuroimaging correlates of these migraine phases allows for an improved comprehension of the underlying changes associated with migraine symptomatology and can assist with evaluation of arising therapeutics for migraine management.

Microdosing psychedelics: More questions than answers? An overview and suggestions for future research

BACKGROUND

In the past few years, the issue of 'microdosing' psychedelics has been openly discussed in the public arena where claims have been made about their positive effect on mood state and cognitive processes such as concentration. However, there are very few scientific studies that have specifically addressed this issue, and there is no agreed scientific consensus on what microdosing is.

AIM

This critique paper is designed to address questions that need to be answered by future scientific studies and to offer guidelines for these studies.

APPROACH

Owing to its proximity for a possible approval in clinical use and short-lasting pharmacokinetics, our focus is predominantly on psilocybin. Psilocybin is allegedly, next to lysergic acid diethylamide (LSD), one of the two most frequently used psychedelics to microdose. Where relevant and available, data for other psychedelic drugs are also mentioned.

CONCLUSION

It is concluded that while most anecdotal reports focus on the positive experiences with microdosing, future research should also focus on potential risks of (multiple) administrations of a psychedelic in low doses. To that end, (pre)clinical studies including biological (e.g. heart rate, receptor turnover and occupancy) as well as cognitive (e.g. memory, attention) parameters have to be conducted and will shed light on the potential negative consequences microdosing could have.

From Mechanism to Cure: Renewing the Goal to Eliminate the Disease of Pain

Objective

Persistent pain causes untold misery worldwide and is a leading cause of disability. Despite its astonishing prevalence, pain is undertreated, at least in part because existing therapeutics are ineffective or cause intolerable side effects. In this review, we cover new findings about the neurobiology of pain and argue that all but the most transient forms of pain needed to avoid tissue damage should be approached as a disease where a cure can be the goal of all treatment plans, even if attaining this goal is not yet always possible.

Design

We reviewed the literature to highlight recent advances in the area of the neurobiology of pain.

Results

We discuss barriers that are currently hindering the achievement of this goal, as well as the development of new therapeutic strategies. We also discuss innovations in the field that are creating new opportunities to treat and even reverse persistent pain, some of which are in late-phase clinical trials.

Conclusion

We conclude that the confluence of new basic science discoveries and development of new technologies are creating a path toward pain therapeutics that should offer significant hope of a cure for patients and practitioners alike. Classification of Evidence. Our review points to new areas of inquiry for the pain field to advance the goal of developing new therapeutics to treat chronic pain.

Calcitonin Gene-Related Peptide Modulators - The History and Renaissance of a New Migraine Drug Class

Several lines of evidence pointed to an important role for CGRP in migraine. These included the anatomic colocalization of CGRP and its receptor in sensory fibers innervating pain-producing meningeal blood vessels, its release by trigeminal stimulation, the observation of elevated CGRP in the cranial circulation during migraine with normalization concomitant with headache relief by sumatriptan, and translational studies with intravenous (IV) CGRP that evoked migraine only in migraineurs. The development of small molecule CGRP receptor antagonists (CGRP-RAs) that showed clinical antimigraine efficacy acutely and prophylactically in randomized placebo-controlled clinical trials subsequently gave definitive pharmacological proof of the importance of CGRP in migraine. More recently, CGRP target engagement imaging studies using a CGRP receptor PET ligand [¹¹ C]MK-4232 demonstrated that there was no brain CGRP receptor occupancy at clinically effective antimigraine doses of telcagepant, a prototypic CGRP-RA. Taken together, these data indicated that (1) the therapeutic site of action of the CGRP-RAs was peripheral not central; (2) that IV CGRP had most likely evoked migraine through an action at sites outside the blood-brain barrier; and (3) that migraine pain was therefore, at least in part, peripheral in origin. The evolution of CGRP migraine science gave impetus to the development of peripherally acting drugs that could modulate CGRP chronically to prevent frequent episodic and chronic migraine. Large molecule biologic antibody (mAb) approaches that are given subcutaneously to neutralize circulating CGRP peptide (fremanezumab, galcanezumab) or block CGRP receptors (erenumab) have shown consistent efficacy and tolerability in multicenter migraine prevention trials and are now approved for clinical use. Eptinezumab, a CGRP neutralizing antibody given IV, shows promise in late stage clinical development. Recently, orally administered next-generation small molecule CGRP-RAs have been shown to have safety and efficacy in acute treatment (ubrogepant and rimegepant) and prevention (atogepant) of migraine, giving additional CGRP-based therapeutic options for migraine patients.

Sumatriptan inhibits the electrophysiological activity of ASICs in rat trigeminal ganglion neurons

Sumatriptan, a selective serotonin 5-HT1 receptor agonist, is an effective therapeutic for migraine attacks. However, the molecular mechanisms underlying sumatriptan migraine relief are still not fully understood. Here, we found that acid-sensing ion channels (ASICs), pH sensors, are peripheral targets of sumatriptan against migraine. Sumatriptan can inhibit the electrophysiological activity of ASICs in the trigeminal ganglion (TG) neurons. In the present study, sumatriptan decreased proton-gated currents mediated by ASICs in a concentration-dependent manner. In addition, sumatriptan shifted concentration-response curves for protons downwards, with a decrease of 37.3 ± 4.6% in the maximum current response but with no significant change in the pH_0.5 value. Sumatriptan inhibition of ASIC currents was blocked by 5-HT_1D receptor antagonist BRL 15572, but not by 5-HT_1B antagonist SB 224289. Moreover, the sumatriptan inhibition of ASICs can be mimicked by the 5-HT_1D receptor agonist L-694,247, but not by the 5-HT_1B agonist CP-93129. Sumatriptan inhibition of ASIC currents was also reversed by G-protein αi subunit inhibitor PTX and 8-Br-cAMP, suggesting the inhibition may involve the intracellular signal transduction. Finally, sumatriptan decreased the number of action potentials induced by acid stimuli in rat TG neurons. Our results indicated that the anti-migraine drug, sumatriptan, inhibited ASICs in rat TG neurons via 5-HT_1D receptor subtype and a cAMP-dependent signal pathway. These observations add to the understanding of the mechanisms that underlie the clinical effectiveness of anti-migraine sumatriptan.

Sumatriptan improves postoperative quality of recovery and reduces postcraniotomy headache after cranial nerve decompression

BACKGROUND

Microvascular decompression (MVD) is a surgical treatment for cranial nerve disorders via a small craniotomy. The postoperative pain of this procedure can be classified as surgical site somatic pain and postcraniotomy headache similar in nature to a migraine, including its association with photophobia, nausea, and vomiting. This headache can be difficult to treat and can impact on postoperative recovery. Sumatriptan is used to treat migraine-like headaches in various settings. This single-centre randomized controlled trial investigated whether postoperative administration of sumatriptan after MVD surgery impacts the quality of postoperative recovery.

METHODS

Fifty patients who complained of postoperative headache after MVD were randomized to receive an s.c. injection of sumatriptan (6 mg) or saline. The primary outcome was quality of recovery as measured by the Quality of Recovery-40 (QoR-40) score at 24 h.

RESULTS

The QoR-40 scores were significantly higher in the sumatriptan group (median 184; interquartile range 169-196) than in the placebo group (133; 119-155; P<0.01), suggesting higher quality of recovery. The sumatriptan group also had significantly lower headache scores at 4, 12, and 24 h. There were no significant differences in other secondary outcomes.

CONCLUSIONS

Use of sumatriptan improved the quality of recovery as measured by the QoR-40 and reduction of headache at 24 h after surgery. Sumatriptan is a useful alternative treatment for postcraniotomy headache. The mechanism remains unknown but could be related to reduction in headache, mood modulation, or both, mediated by a serotonin effect.

CLINICAL TRIAL REGISTRATION

NCT01632657.

Is selective 5-HT1F receptor agonism an entity apart from that of the triptans in antimigraine therapy?

Migraine is a neurovascular disorder that involves activation of the trigeminovascular system and cranial vasodilation mediated by release of calcitonin gene-related peptide (CGRP). The gold standard for acute migraine treatment are the triptans, 5-HT1B/1D/(1F) receptor agonists. Their actions are thought to be mediated through activation of: (i) 5-HT1B receptors in cranial blood vessels with subsequent cranial vasoconstriction; (ii) prejunctional 5-HT1D receptors on trigeminal fibers that inhibit trigeminal CGRP release; and (iii) 5-HT1B/1D/1F receptors in central nervous system involved in (anti)nociceptive modulation. Unfortunately, coronary arteries also express 5-HT1B receptors whose activation would produce coronary vasoconstriction; hence, triptans are contraindicated in patients with cardiovascular disease. In addition, since migraineurs have an increased cardiovascular risk, it is important to develop antimigraine drugs devoid of vascular (side) effects. Ditans, here defined as selective 5-HT1F receptor agonists, were developed on the basis that most of the triptans activate trigeminal 5-HT1F receptors, which may explain part of the triptans' antimigraine action. Amongst the ditans, lasmiditan: (i) fails to constrict human coronary arteries; and (ii) is effective for the acute treatment of migraine in preliminary Phase III clinical trials. Admittedly, the exact site of action is still unknown, but lasmiditan possess a high lipophilicity, which suggests a direct action on the central descending antinociceptive pathways. Furthermore, since 5-HT1F receptors are located on trigeminal fibers, they could modulate CGRP release. This review will be particularly focussed on the similarities and differences between the triptans and the ditans, their proposed sites of action, side effects and their cardiovascular risk profile.

Current and novel insights into the neurophysiology of migraine and its implications for therapeutics

Migraine headache and its associated symptoms have plagued humans for two millennia. It is manifest throughout the world, and affects more than 1/6 of the global population. It is the most common brain disorder, and is characterized by moderate to severe unilateral headache that is accompanied by vomiting, nausea, photophobia, phonophobia, and other hypersensitive symptoms of the senses. While there is still a clear lack of understanding of its neurophysiology, it is beginning to be understood, and it seems to suggest migraine is a disorder of brain sensory processing, characterized by a generalized neuronal hyperexcitability. The complex symptomatology of migraine indicates that multiple neuronal systems are involved, including brainstem and diencephalic systems, which function abnormally, resulting in premonitory symptoms, ultimately evolving to affect the dural trigeminovascular system, and the pain phase of migraine. The migraineur also seems to be particularly sensitive to fluctuations in homeostasis, such as sleep, feeding and stress, reflecting the abnormality of functioning in these brainstem and diencephalic systems. Implications for therapeutic development have grown out of our understanding of migraine neurophysiology, leading to major drug classes, such as triptans, calcitonin gene-related peptide receptor antagonists, and 5-HT1F receptor agonists, as well as neuromodulatory approaches, with the promise of more to come. The present review will discuss the current understanding of the neurophysiology of migraine, particularly migraine headache, and novel insights into the complex neural networks responsible for associated neurological symptoms, and how interaction of these networks with migraine pain pathways has implications for the development of novel therapeutics.

Intranasal Eutectic Powder of Zolmitriptan with Enhanced Bioavailability in the Rat Brain

Intranasal administration can potentially deliver drugs to the brain because of the proximity of the delivery site to the olfactory lobe. We prepared triturates of micronized or crystalline zolmitriptan with a GRAS substance, nicotinamide, to form a eutectic. We characterized the formulation using differential scanning calorimetry, powder X-ray diffraction, and FTIR spectroscopy to confirm its eutectic nature and generated a phase diagram. The eutectic formulation was aerosolized using an in-house insufflator into the nares of rats. Groups of rats received zolmitriptan intravenously or intranasally, or intranasal eutectic formulation. Zolmitriptan was estimated in the olfactory lobe, cerebral cortex, cerebellum, and blood plasma at different time-points by LC-MS. Pharmacokinetics in these tissues indicated the superiority of the intranasal eutectic formulation for brain targeting when compared with results of IV solution and intranasal pure zolmitriptan powder. Enhancement of nose-to-brain transport is likely to have resulted from more rapid dissolution of the eutectic as compared to pure drug.

Naratriptan Has a Selective Inhibitory Effect on Trigeminovascular Neurones at Central 5-HT1A and 5-HT1B/1D Receptors in the Cat: Implications for Migraine Therapy

The triptans are agonists at serotonin(5-HT) 1B/1D receptors; however, they are also active at 5-HT1A and 5-HT1F receptors. We conducted this series of experiments to further elucidate the site of action of naratriptan using a well-established animal model of trigeminovascular stimulation. Following electrical stimulation of the superior sagittal sinus of the cat, single cell responses ( n = 83) were recorded in the trigeminal nucleus caudalis. Most cells (91%) also responded to electrical and mechanical stimulation of cutaneous or mucosal facial receptive fields. The micro-iontophoretic application of naratriptan resulted in a significant suppression of the response to sagittal sinus stimulation (response suppressed by 47 ± 4%, P < 0.001). The effect of naratriptan was significantly attenuated by application of either the 5-HT1B/1D receptor antagonist GR-127935 ( P < 0.001) or the 5-HT1A antagonist WAY-100635 ( P < 0.05). The response of single cells to receptive field stimulation was also suppressed by microiontophoretic application of naratriptan, but by only 20 ± 3%. Intravenous administration of naratriptan resulted in a similar selective suppression of sagittal sinus vs. receptive field responses in trigeminal neurones. These results indicate that naratriptan has a central effect in the trigeminovascular system, selectively inhibiting afferent activity in craniovascular neurones, via both 5-HT1B/1D and 5-HT1A receptors.

Blockade of CGRP Receptors in the Intracranial Vasculature: A New Target in the Treatment of Headache

In primary headaches, there is a clear association between the headache and the release of calcitonin gene-related peptide (CGRP) but not with any of the other neuronal messengers. The purpose of this review is to describe the role of CGRP in the intracranial circulation and to elucidate a possible role for a specific CGRP receptor antagonist in the treatment of primary headaches. Acute treatment with a 5-HT1B/1D agonist (triptan) results in alleviation of the headache and normalization of the cranial venous CGRP levels, in part due to a presynaptic inhibitory effect on sensory nerves. The central role of CGRP in migraine and cluster headache pathophysiology has led to the search for small molecule CGRP antagonists with few cardiovascular side-effects. The initial pharmacological profile of such a group of compounds has recently been disclosed. One of these compounds has been found to be efficacious in the relief of acute attacks of migraine.

Hypoxia facilitates neurogenic dural plasma protein extravasation in mice: a novel animal model for migraine pathophysiology

Migraine animal models generally mimic the onset of attacks and acute treatment processes. A guinea pig model used the application of meta-chlorophenylpiperazine (mCPP) to trigger immediate dural plasma protein extravasation (PPE) mediated by 5-HT_2B receptors. This model has predictive value for antimigraine drugs but cannot explain the delayed onset of efficacy of 5-HT_2B receptor antagonists when clinically used for migraine prophylaxis. We found that mCPP failed to induce dural PPE in mice. Considering the role 5-HT_2B receptors play in hypoxia-induced pulmonary vessel muscularization, we were encouraged to keep mice under hypoxic conditions and tested whether this treatment will render them susceptible to mCPP-induced dural PPE. Following four-week of hypoxia, PPE, associated with increased transendothelial transport, was induced by mCPP. The effect was blocked by sumatriptan. Chronic application of 5-HT_2B receptor or nitric oxide synthase blockers during hypoxia prevented the development of susceptibility. Here we present a migraine model that distinguishes between a migraine-like state (hypoxic mice) and normal, normoxic mice and mimics processes that are related to chronic activation of 5-HT_2B receptors under hypoxia. It seems striking, that chronic endogenous activation of 5-HT_2B receptors is crucial for the sensitization since 5-HT_2B receptor antagonists have strong, albeit delayed migraine prophylactic efficacy.

Headache, cerebral aneurysms, and the use of triptans and ergot derivatives

BACKGROUND

Uncertainty exists regarding the correlation between unruptured cerebral aneurysms and their role in headache etiology. It is also unclear whether surgical endovascular treatment may improve or worsen the headache, and if there are predictable factors for headache outcome such as pre-existing headache features, aneurysm characteristics, or other medical history. There is debate regarding safe treatment of migraine in patients with aneurysms, both before and after endovascular treatments. Particularly, there is hesitancy to use the triptans and ergot derivatives such as dihydroergotamine because of their vasoconstrictive effects and concern for adverse events related to the aneurysm such as aneurysmal instability and rupture.

OBJECTIVE

To review the literature regarding the anatomy, pathophysiology, and association between headache, untreated vs surgically treated aneurysms, and the use of triptans and ergot derivatives for migraine treatment in this setting.

CONCLUSION

Associations between some headaches and aneurysms may exist. Some chronic headaches may respond to surgical aneurysm repair while others may worsen. These associations are undefined by current literature because of variable results, study methods, and limited data. Prospective studies are needed which incorporate pre- and post-procedure headache character and diagnosis, aneurysm characteristics, type of aneurysm repair, associated risk factors for worsening post-procedure headache, and ultimately combining all of these data to better predict headache outcome following surgical aneurysm treatment. Lastly, the caution and avoidance of triptan and ergot derivative use for migraine in the setting of aneurysm is not supported by the current evidence, and much of this concern may be excessive and unwarranted, although more evidence confirming safety is needed.

Orofacial pain management: current perspectives

Some of the most prevalent and debilitating pain conditions arise from the structures innervated by the trigeminal system (head, face, masticatory musculature, temporomandibular joint and associated structures). Orofacial pain (OFP) can arise from different regions and etiologies. Temporomandibular disorders (TMD) are the most prevalent orofacial pain conditions for which patients seek treatment. Temporomandibular disorders include a number of clinical problems that involve the masticatory musculature, the temporomandibular joint (TMJ) or both. Trigeminal neuropathic pain conditions can arise from injury secondary to dental procedures, infection, neoplasias, or disease or dysfunction of the peripheral and/or central nervous system. Neurovascular disorders, such as primary headaches, can present as chronic orofacial pain, such as in the case of facial migraine, where the pain is localized in the second and third division of the trigeminal nerve. Together, these disorders of the trigeminal system impact the quality of life of the sufferer dramatically. A multidisciplinary pain management approach should be considered for the optimal treatment of orofacial pain disorders including both non-pharmacological and pharmacological modalities.

BMS-927711 for the acute treatment of migraine: a double-blind, randomized, placebo controlled, dose-ranging trial

BACKGROUND

BMS-927711 is a potent, selective, competitive human calcitonin gene-related peptide (CGRP) receptor antagonist that has shown in vivo efficacy without vasoconstrictor effect. The objective of the current study was to determine an effective and tolerable dose range of BMS-927711 for the acute treatment of migraine.

METHODS

In this randomized, double-blind, placebo controlled, dose-ranging study, 885 patients were randomized using an adaptive design to one of the following dose groups: BMS-927711 (10, 25, 75, 150, 300, or 600 mg); sumatriptan 100 mg (active comparator); and placebo. Patients were treated for a single migraine attack. The primary endpoint was pain freedom at two hours post-dose.

RESULTS

Of patients who took the study drug, 799 had one post-randomization efficacy evaluation. Significantly more patients in the BMS-927711 75 mg (31.4%, P = 0.002), 150 mg (32.9%, P < 0.001), and 300 mg (29.7%, P = 0.002) groups and the sumatriptan group (35%, P < 0.001) had pain freedom at two hours post-dose versus placebo (15.3%). For the secondary endpoint of sustained pain freedom from two to 24 hours post-dose, BMS-927711 doses (25-600 mg) were also statistically significant compared with placebo. No deaths or treatment-related serious adverse events (AEs) were reported, and no patients discontinued because of AEs.

CONCLUSIONS

BMS-927711 is superior to placebo at several different doses (75 mg, 150 mg, and 300 mg) and has an excellent tolerability profile.

Pathophysiology of Migraine

Migraine is a serious health problem which impair quality of life. It is the second most common primary headache that affects approximately more than %10 people in general population. Migraine pathophysiology is still unclear. Increasing results of studies suggest to migraine pathophysiology is related with primary neuronal mechanisms. Migraine pain starts in which region of brain and what brain regions are activated in different stages is unenlightened. There is evidences that growing number of studies which using new imaging techniques as positron emission tomography (PET) and functional magnetic resonans imaging (fMRI) show that migraine and cluster headaches are related with neuronal structures and vasodilatation. There are four phases to a migraine. The prodrome phase, aura, the attack, and the postdrome phase. Some datas obtained from last ten years indicate that cortical excitability has increased in interictal phase too. For many years, studies in rodents show trgimenial nerve is activated and it leads to vasodilatation and neurogenic inflammation in the headache phase. Although the majority of patients encountered in clinical practice are migraine without aura or chronic migraine, experimental studies of the migraine pathophysiology are focusing on the aura model which is used cortical spreading depression.

5-HT(1B) receptors inhibit glutamate release from primary afferent terminals in rat medullary dorsal horn neurons

BACKGROUND AND PURPOSE

Although 5-HT(1B) receptors are expressed in trigeminal sensory neurons, it is still not known whether these receptors can modulate nociceptive transmission from primary afferents onto medullary dorsal horn neurons.

EXPERIMENTAL APPROACH

Primary afferent-evoked EPSCs were recorded from medullary dorsal horn neurons of rat horizontal brain stem slices using a conventional whole-cell patch clamp technique under a voltage-clamp condition.

KEY RESULTS

CP93129, a selective 5-HT(1B) receptor agonist, reversibly and concentration-dependently decreased the amplitude of glutamatergic EPSCs and increased the paired-pulse ratio. In addition, CP93129 reduced the frequency of spontaneous miniature EPSCs without affecting the current amplitude. The CP93129-induced inhibition of EPSCs was significantly occluded by GR55562, a 5-HT(1B/1D) receptor antagonist, but not LY310762, a 5-HT(1D) receptor antagonist. Sumatriptan, an anti-migraine drug, also decreased EPSC amplitude, and this effect was partially blocked by either GR55562 or LY310762. On the other hand, primary afferent-evoked EPSCs were mediated by the Ca(2+) influx passing through both presynaptic N-type and P/Q-type Ca(2+) channels. The CP93129-induced inhibition of EPSCs was significantly occluded by ω-conotoxin GVIA, an N-type Ca(2+) channel blocker.

CONCLUSIONS AND IMPLICATIONS

The present results suggest that the activation of presynaptic 5-HT(1B) receptors reduces glutamate release from primary afferent terminals onto medullary dorsal horn neurons, and that 5-HT(1B) receptors could be, at the very least, a potential target for the treatment of pain from orofacial tissues.

Emerging target-based paradigms to prevent and treat migraine

Migraine is a primary brain disorder resulting from altered modulation of normal sensory stimuli and trigeminal nerve dysfunction. The second edition of the International Classification of Headache Disorders (ICHD-2) defines seven subtypes of migraine. Migraine treatment can be acute or preventive. New targeted therapies include 5-HT(1F) receptor agonists, calcitonin gene-related peptide (CGRP) antagonists, nitric oxide synthetase inhibitors, and ion channel antagonists. A recent development is the creation of antibodies to CGRP and its receptor for migraine prevention.

Sumatriptan inhibition of N-type calcium channel mediated signaling in dural CGRP terminal fibres

The selective 5-HT₁ receptor agonist sumatriptan is an effective therapeutic for migraine pain yet the antimigraine mechanisms of action remain controversial. Pain-responsive fibres containing calcitonin gene-related peptide (CGRP) densely innervating the cranial dura mater are widely believed to be an essential anatomical substrate for the development of migraine pain. 5-HT₁ receptors in the dura colocalize with CGRP fibres in high density and thus provide a possible peripheral site of action for sumatriptan. In the present study, we used high-resolution optical imaging selectively within individual mouse dural CGRP nociceptive fibre terminations and found that application of sumatriptan caused a rapid, reversible dose-dependent inhibition in the amplitude of single action potential evoked Ca²⁺ transients. Pre-application of the 5-HT₁ antagonist GR 127935 or the selective 5-HT(1D) antagonist BRL 15572 prevented inhibition while the selective 5-HT(1B) antagonist SB 224289 did not, suggesting this effect was mediated selectively through the 5-HT(1D) receptor subtype. Sumatriptan inhibition of the action potential evoked Ca²⁺ signaling was mediated selectively through N-type Ca²⁺ channels. Although the T-type Ca²⁺ channel accounted for a greater proportion of the Ca²⁺ signal it did not mediate any of the sumatriptan inhibition. Our findings support a peripheral site of action for sumatriptan in inhibiting the activity of dural pain fibres selectively through a single Ca²⁺ channel subtype. This finding adds to our understanding of the mechanisms that underlie the clinical effectiveness of 5-HT₁ receptor agonists such as sumatriptan and may provide insight for the development of novel peripherally targeted therapeutics for mitigating the pain of migraine.

Trigeminocervical complex responses after lesioning dopaminergic A11 nucleus are modified by dopamine and serotonin mechanisms

Both serotonergic and dopaminergic receptor modulation can alter trigeminal nociceptive processing, and descending A11 dopaminergic projections can affect trigeminal nociceptive transmission. Here we aimed to test the interaction between dopamine D(2) and serotonin 5-HT(1B/1D) receptors and their individual and combined effects in order to better understand the relationship of the descending influences of these systems on nociceptive trigeminovascular afferents. Extracellular recordings were made in the rat trigeminocervical complex in response to electrical stimulation of the dura mater and mechanical noxious and innocuous stimulation of the ipsilateral ophthalmic dermatome. The A11 nucleus was lesioned, and following the resultant facilitation of neuronal firing, one of a selective 5-HT(1B/1D) receptor agonist (naratriptan), selective 5-HT(1B/1D) receptor antagonist (GR127935), a selective D(2)-like receptor agonist (quinpirole), and a selective D(1)-like receptor agonist (dihydrexidine), or a combination of the above, were administered. Both quinpirole and quinpirole with naratriptan inhibited firing in the trigeminocervical complex evoked by noxious stimuli, reducing it below prelesion baseline, while the response to innocuous stimuli was reduced back to baseline. Both naratriptan alone, and quinpirole combined with GR127935, inhibited firing in the trigeminocervical complex evoked by noxious stimuli, returning it to prelesion baseline, while the response to innocuous stimuli remained facilitated. Immunohistochemical staining demonstrated D(2)-receptor and 5-HT(1B/1D)-receptor colocalization in the trigeminocervical complex. The data suggest that the serotonergic and dopaminergic antinociceptive pathways act simultaneously on neurons in the trigeminocervical complex, and both amine systems need to be functioning for trigeminal sensitization to be reversed.

Sex differences in the inflammatory mediator-induced sensitization of dural afferents

Approximately 20% of the adult population suffers from migraine. This debilitating pain disorder is three times more prevalent in women than in men. To begin to evaluate the underlying mechanisms that may contribute to this sex difference, we tested the hypothesis that there is a sex difference in the inflammatory mediator (IM)-induced sensitization of dural afferents. Acutely dissociated retrogradely labeled dural afferents from adult Sprague-Dawley rats were examined with whole cell patch-clamp recordings. Baseline passive and active electrophysiological properties of dural afferents from both sexes were comparable. However, while IM-induced increases in the excitability of dural afferents from male and female rats were also comparable, the proportion of dural afferents from female rats sensitized by IM (~100%) was significantly greater than that of dural afferents from male rats (~50%). This appeared to be due to differences downstream of IM receptors, as tetrodotoxin-resistant sodium current was increased by IM in a majority of male dural afferents (13/14). These data indicate that there are both quantitative and qualitative differences in the IM-induced sensitization of dural afferents that may contribute to the sex difference in the manifestation of migraine.

5-HT(1D) receptor immunoreactivity in the sphenopalatine ganglion: implications for the efficacy of triptans in the treatment of autonomic signs associated with cluster headache

OBJECTIVE

To determine if 5-HT(1D) receptors are located in the sphenopalatine ganglion.

BACKGROUND

While the 5-HT(1D) receptor has been described in sensory and sympathetic ganglia in the head, it was not known whether they were also located in parasympathetic ganglia.

METHODS

We used retrograde labeling combined with immunohistochemistry to examine 5-HT(1D) receptor immunoreactivity in rat sphenopalatine ganglion neurons that project to the lacrimal gland, nasal mucosa, cerebral vasculature, and trigeminal ganglion.

RESULTS

We found 5-HT(1D) receptor immunoreactivity in nerve terminals around postganglionic cell bodies within the sphenopalatine ganglion. All 5-HT(1D) -immunoreactive terminals were also immunoreactive for calcitonin gene-related peptide but not vesicular acetylcholine transporter, suggesting that they were sensory and not preganglionic parasympathetic fibers. Our retrograde labeling studies showed that approximately 30% of sphenopalatine ganglion neurons innervating the lacrimal gland, 23% innervating the nasal mucosa, and 39% innervating the trigeminal ganglion were in apparent contact with 5-HT(1D) receptor containing nerve terminals.

CONCLUSION

These data suggest that 5-HT(1D) receptors within primary afferent neurons that innervate the sphenopalatine ganglion are in a position to modulate the excitability of postganglionic parasympathetic neurons that innervate the lacrimal gland and nasal mucosa, as well as the trigeminal ganglion. This has implications for triptan (5-HT(1D) receptor agonist) actions on parasympathetic symptoms in cluster headache.

Peripheral targets of 5-HT(1D) receptor immunoreactive trigeminal ganglion neurons

OBJECTIVE

The aim of the current study was to determine the proportion of trigeminal primary afferent neurons that innervate the intracranial vasculature, and other craniofacial tissues, that are also 5 hydroxy triptamine (5-HT)(1D) receptor immunoreactive.

METHODS

Retrograde tracing and immunohistochemistry was used to identify 5-HT(1D) receptor labeled trigeminal primary afferent neurons that innervate the lacrimal gland (n = 3 animals), nasal mucosa (n = 3 animals), and the intracranial vasculature (middle meningeal artery in the dura [n = 3 animals] and middle cerebral artery [n = 3 animals]).

RESULTS

The percentage of neurons that were 5-HT(1D) receptor immunoreactive was greater for primary afferent neurons innervating the middle meningeal artery (41.8 ± 1%) than those innervating the middle cerebral artery (28.4 ± 0.8%), nasal mucosa (25.6 ± 1%), or lacrimal gland (23.5 ± 3%). For each retrograde labeled population, the 5-HT(1D) receptor immunoreactive cells were among the smallest of the retrograde labeled cells.

CONCLUSIONS

These findings provide a basis for understanding the role of 5-HT(1D) receptor agonists (eg, triptans) in the treatment of primary vascular headaches and suggest that the selectivity of triptans in the treatment of these headaches does not appear to result from specific localization of the 5-HT(1D) receptor to trigeminovascular neurons alone.

Human cerebrovascular contractile receptors are upregulated via a B-Raf/MEK/ERK-sensitive signaling pathway

Background

Cerebral ischemia results in a rapid increase in contractile cerebrovascular receptors, such as the 5-hydroxytryptamine type 1B (5-HT_1B), angiotensin II type 1 (AT₁), and endothelin type B (ET_B) receptors, in the vessel walls within the ischemic region, which further impairs local blood flow and aggravates tissue damage. This receptor upregulation occurs via activation of the mitogen-activated protein kinase pathway. We therefore hypothesized an important role for B-Raf, the first signaling molecule in the pathway. To test our hypothesis, human cerebral arteries were incubated at 37°C for 48 h in the absence or presence of a B-Raf inhibitor: SB-386023 or SB-590885. Contractile properties were evaluated in a myograph and protein expression of the individual receptors and activated phosphorylated B-Raf (p-B-Raf) was evaluated immunohistochemically.

Results

5-HT_1B, AT₁, and ET_B receptor-mediated contractions were significantly reduced by application of SB-590885, and to a smaller extent by SB-386023. A marked reduction in AT₁ receptor immunoreactivity was observed after treatment with SB-590885. Treatment with SB-590885 and SB-386023 diminished the culture-induced increase of p-B-Raf immunoreactivity.

Conclusions

B-Raf signaling has a key function in the altered expression of vascular contractile receptors observed after organ culture. Therefore, specific targeting of B-Raf might be a novel approach to reduce tissue damage after cerebral ischemia by preventing the previously observed upregulation of contractile receptors in smooth muscle cells.

Distribution of 5-HT(1B), 5-HT(1D) and 5-HT(1F) receptor expression in rat trigeminal and dorsal root ganglia neurons: relevance to the selective anti-migraine effect of triptans

Triptans, acting as serotonin, 5-HT(1B/1D/1F), receptor agonists, provide an effective and established treatment option in migraine and cluster headache. Clinical observations suggest a relatively specific effect of these compounds on primary headache disorders, but not in other pain syndromes. The mechanism of this specificity, however, is not well understood. Hence, we systematically studied primary sensory ganglia in rat to determine if the peripheral distribution of 5HT(1B/1D/1F) receptors showed any anatomical difference that would account for the specificity of clinical effect. Rat primary afferent and sensory ganglia neurons--trigeminal ganglia (Vg), and dorsal root ganglia (DRG): C(2), C(5), T(5), L(5)--were examined using paraffin-embedded, slide-bound tissue sections reacted with specific primary antibodies for rat 5-HT(1B, 1D) and (1F) receptors in a peroxidase-based immunohistochemical method. Immunoreactivity specific for all three serotonergic receptor subtypes was demonstrated in the five peripheral nervous system regions examined and quantitated. There was a good agreement for 5-HT(1B) and 5-HT(1D) receptors to that previously demonstrated in Vg and DRG L(5), while this was the first characterisation for 5-HT(1F) receptor in any of the five regions, as well as for 5-HT(1B) and 5HT(1D) receptors in DRG C(2), C(5) and T(5). In summary, all three 5-HT receptors are equally represented in Vg and the DRGs examined. We conclude that the triptans are theoretically able to bind to receptors at each level of the peripheral neuraxis without any apparent anatomical preference for the head.

The relevance of preclinical research models for the development of antimigraine drugs: focus on 5-HT(1B/1D) and CGRP receptors

Migraine is a complex neurovascular syndrome, causing a unilateral pulsating headache with accompanying symptoms. The past four decades have contributed immensely to our present understanding of migraine pathophysiology and have led to the introduction of specific antimigraine therapies, much to the relief of migraineurs. Pathophysiological factors culminating into migraine headaches have not yet been completely deciphered and, thus, pose an additional challenge for preclinical research in the absence of any direct experimental marker. Migraine provocation experiments in humans use a head-score to evaluate migraine, as articulated by the volunteer, which cannot be applied to laboratory animals. Therefore, basic research focuses on different symptoms and putative mechanisms, one at a time or in combination, to validate the hypotheses. Studies in several species, utilizing different preclinical approaches, have significantly contributed to the two antimigraine principles in therapeutics, namely: 5-HT(1B/1D) receptor agonists (known as triptans) and CGRP receptor antagonists (known as gepants). This review will analyze the preclinical experimental models currently known for the development of these therapeutic principles, which are mainly based on the vascular and/or neurogenic theories of migraine pathogenesis. These include models based on the involvement of cranial vasodilatation and/or the trigeminovascular system in migraine. Clearly, the preclinical strategies should involve both approaches, while incorporating the newer ideas/techniques in order to get better insights into migraine pathophysiology.

Pharmacology

Headache treatment has been based primarily on experiences with non-specific drugs such as analgesics, non-steroidal anti-inflammatory drugs, or drugs that were originally developed to treat other diseases, such as beta-blockers and anticonvulsant medications. A better understanding of the basic pathophysiological mechanisms of migraine and other types of headache has led to the development over the past two decades of more target-specific drugs. Since activation of the trigeminovascular system and neurogenic inflammation are thought to play important roles in migraine pathophysiology, experimental studies modeling those events successfully predicted targets for selective development of pharmacological agents to treat migraine. Basically, there are two fundamental strategies for the treatment of migraine, abortive or preventive, based to a large degree on the frequency of attacks. The triptans, which exhibit potency towards selective serotonin (5-hydroxytryptamine, 5-HT) receptors expressed on trigeminal nerves, remain the most effective drugs for the abortive treatment of migraine. However, numerous preventive medications are currently available that modulate the excitability of the nervous system, particularly the cerebral cortex. In this chapter, the pharmacology of commercially available medications as well as drugs in development that prevent or abort headache attacks will be discussed.

Neurons of the dopaminergic/calcitonin gene-related peptide A11 cell group modulate neuronal firing in the trigeminocervical complex: an electrophysiological and immunohistochemical study

Activation of spinal trigeminal afferents innervating the cranial vasculature is likely to play a role in migraine, although some parts of the clinical presentation may have a dopaminergic basis. The A11 nucleus, located in the posterior hypothalamus, provides the only known source of descending dopaminergic innervation for the spinal gray matter. Extracellular recordings were made in the trigeminocervical complex (TCC) in response to electrical stimulation of the dura mater. Receptive fields were characterized by mechanical noxious and innocuous stimulation of the ipsilateral ophthalmic dermatome. Stimulation of the A11 significantly inhibited peri-middle meningeal artery dural and noxious pinch evoked firing of neurons in the TCC. This inhibition was reversed by the D(2) receptor antagonist eticlopride. Lesioning of the A11 significantly facilitated dural and noxious pinch and innocuous brush evoked firing from the TCC. In previous work using immunohistofluorescence, it was shown that D(1) and D(2) receptors were found in the rat TCC, and here we report, in addition, that D(4) and D(5) dopamine receptors are also present, whereas D(3) receptors are not. No dopamine receptors were present in the A11 nucleus itself. However, the A11 does contain dopamine and calcitonin gene-related peptide (CGRP) and, by this combination, is distinct from the neighboring CGRPergic subparafascicular nucleus. Exploration of dopaminergic influences and mechanisms in migraine may open up an almost untapped opportunity to pursue potential new therapeutic options for the disorder.

Migraine: an overview

The pathophysiology of migraine is not completely understood and continues to be investigated. The complexity of interactions taking place in the sensory neuronal network with the mediation of all different neurotransmitters involved gives the measure of the extreme difficulty connected with the knowledge of migraine pathogenesis and in particular of its cardinal sign. Neuronal components are relevant in migraine pathophysiology: there could be a generalized interictal abnormal excitability of the cerebral cortex in migraine, possibly favoring the occurrence of spreading depression with consequent activation of the trigeminal system. Many theories have been formulated in these last sixty years about the pathogenesis of migraine and other forms of primary headache, but the problem is still far to be fully clarified. The present review is focused on the description of different theories on the migraine pathogenesis. This review is dedicated to the memory of Prof. Alfredo Bianchi.

5-HT2 receptors modulate excitatory neurotransmission to cardiac vagal neurons within the nucleus ambiguus evoked during and after hypoxia

To examine the role of 5-HT2 receptors in the central cardiorespiratory network, and in particular the respiratory modulation of parasympathetic activity to the heart, we used an in vitro medullary slice that allowed simultaneous examination of rhythmic inspiratory-related activity recorded from hypoglossal rootlet and excitatory inspiratory-related neurotransmission to cardioinhibitory vagal neurons (CVNs) within the nucleus ambiguus (NA). Focal application of ketanserin, a 5-HT2 receptor antagonist, did not significantly alter the frequency of spontaneous excitatory postsynaptic excitatory currents (EPSCs) in CVNs in control conditions. However, ketanserin diminished spontaneous excitatory neurotransmission to CVNs during hypoxia. The inhibitory action of ketanserin was on 5-HT3 mediated EPSCs during hypoxia since these responses were blocked by the 5-HT3 receptor antagonist ondansetron. In addition, a robust inspiratory-related excitatory neurotransmission was recruited during recovery from hypoxia. Focal application of ketanserin during this posthypoxia period evoked a significant augmentation of the frequency of inspiratory-related, but not spontaneous EPSCs in CVNs. This excitatory effect of ketanserin was prevented by application of the purinergic receptor blocker pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS). These results demonstrate 5-HT2 receptors differentially modulate excitatory neurotransmission to CVNs during and after hypoxia. Activation of 5-HT2 receptors acts to maintain excitatory neurotransmission to CVNs during hypoxia, likely via presynaptic facilitation of 5-HT3 receptor-mediated neurotransmission to CVNs. However, activation of 5HT2 receptors diminishes the subsequent inspiratory-related excitatory neurotransmission to CVNs that is recruited during the recovery from hypoxia likely exerting an inhibitory action on inspiratory-related purinergic signaling.

The triptans

The migraine-specific triptans have revolutionized the treatment of migraine and are currently the drugs of choice to treat a migraine attack in progress. Over the past 15 years, triptans were released in rapid succession, with each one demonstrating some specific pharmacokinetic properties that may be translated into clinical advantages. Triptans share many similarities, but also have important differences from one another. Accordingly, herein we discuss the class of the triptans. We first define the trigeminovascular system and its importance in migraine pain, then discuss the mechanism of action of the triptans and contrast the evidence supporting the use of different triptans. We close with our view of the future and hopes for the next generation of antimigraine therapies.

Inhibition of calcitonin gene-related peptide function: a promising strategy for treating migraine

The neuropeptide calcitonin gene-related peptide (CGRP) is implicated in the underlying pathology of migraine. Serum levels of CGRP, which are elevated during a migraine attack, have been reported to return to normal with alleviation of pain. In addition, CGRP administration has been shown to cause a migraine-like headache in susceptible individuals. Importantly, CGRP receptors are found on many cell types within the trigeminovascular system that are thought to play important roles in controlling inflammatory and nociceptive processes. Based on these findings, it was proposed that blockage of CGRP receptor function and, hence, the physiological effects of CGRP would be effective in aborting a migraine attack. This review will summarize key preclinical data that support the therapeutic potential of using CGRP receptor antagonists or molecules that bind CGRP within the context of current neurovascular theories on migraine pathology.

Ten years of rizatriptan: from development to clinical science and future directions

The year 2008 marked the 10th anniversary since rizatriptan was first launched for the acute treatment of migraine. In this article we discuss the concepts that motivated the preclinical and clinical development of rizatriptan, the clinical evidence that has driven its use over the past decade, rizatriptan's overall contribution to the field, and future directions for research.

Migraine, allodynia, and implications for treatment

Allodynia--perception of pain from non-noxious stimuli--is a common clinical feature in various pain syndromes. The significance for migraine has increasingly been recognized and the pathophysiology has been investigated in detail. Allodynia is a marker for sensitization of central trigeminal neurons. Intensity and persistence of allodynic symptoms are a function of duration of migraine attacks, frequency of attacks, and migraine history. It has been hypothesized that treatment success with triptans may be severely impaired in the presence of allodynia. However, randomized controlled trials did not confirm that. Treatment with cyclooxygenase inhibitors and dihydroergotamine does not seem to be limited by allodynia; these medications may be able to reverse allodynia. Data on the new class of calcitonin-gene related-peptide antagonists are not yet available. Additional and more refined randomized controlled trials, focusing on methodological issues pertaining to the determination of allodynia, are warranted to resolve the true relationship between allodynia and treatment response. Regardless--based on available randomized controlled trials--the recommendation prevails to initiate abortive treatment as soon as possible after attack onset when pain is still mild.

Investigation of the immunoreactivities of NOS enzymes and the effect of sumatriptan in adolescent rats using an experimental model of migraine

The aim was to investigate the immunoreactivities for NOS enzymes in frontal cortex and meningeal vessels after chemical stimulation of the subarachnoid space of adolescent rats and the effect of sumatriptan pre-treatment on the immunoreactivities of the NOS enzymes. Male adolescent Wistar rats were used. Rats in group 1 did not taken intracisternal injection. Rats in group 2 were taken intracisternal autologous blood injection, but no sumatriptan pre-treatment. Rats in group 3 were taken intracisternal autologous blood injection, but they were taken sumatriptan pre-treatment. Tissue samples were investigated for the presence of NOS immunoreactivity. The mean values of immunolabeling intensities for NOS enzymes in frontal cortex and meningeal vessels were significantly increased in group 2 compared to group 1. The mean values of immunolabeling intensities for NOS enzymes in frontal cortex and meningeal vessels were significantly reduced in group 3 compared to group 2. These results suggest that, chemical stimulation of the subarachnoid space increased the immunoreactivities of NOS enzymes in the brain of adolescent rats. The increased NOS immunoreactivities could be antagonized by pre-treatment with sumatriptan.