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

Management of cluster headache: Treatments and their mechanisms

BACKGROUND

The management of cluster headache is similar to that of other primary headache disorders and can be broadly divided into acute and preventive treatments. Acute treatments for cluster headache are primarily delivered via rapid, non-oral routes (such as inhalation, nasal, or subcutaneous) while preventives include a variety of unrelated treatments such as corticosteroids, verapamil, and galcanezumab. Neuromodulation is becoming an increasingly popular option, both non-invasively such as vagus nerve stimulation when medical treatment is contraindicated or side effects are intolerable, and invasively such as occipital nerve stimulation when medical treatment is ineffective. Clinically, this collection of treatment types provides a range of options for the informed clinician. Scientifically, this collection provides important insights into disease mechanisms.

METHODS

Two authors performed independent narrative reviews of the literature on guideline recommendations, clinical trials, real-world data, and mechanistic studies.

RESULTS

Cluster headache is treated with acute treatments, bridge treatments, and preventive treatments. Common first-line treatments include subcutaneous sumatriptan and high-flow oxygen as acute treatments, corticosteroids (oral or suboccipital injections) as bridge treatments, and verapamil as a preventive treatment. Some newer acute (non-invasive vagus nerve stimulation) and preventive (galcanezumab) treatments have excellent clinical trial data for episodic cluster headache, while other newer treatments (occipital nerve stimulation) have been specifically tested in treatment-refractory chronic cluster headache. Most treatments are suspected to act on the trigeminovascular system, the autonomic system, or the hypothalamus.

CONCLUSIONS

The first-line treatments have not changed in recent years, but new treatments have provided additional options for patients.

Therapeutic applications and potential mechanisms of acupuncture in migraine: A literature review and perspectives

Acupuncture is commonly used as a treatment for migraines. Animal studies have suggested that acupuncture can decrease neuropeptides, immune cells, and proinflammatory and excitatory neurotransmitters, which are associated with the pathogenesis of neuroinflammation. In addition, acupuncture participates in the development of peripheral and central sensitization through modulation of the release of neuronal-sensitization-related mediators (brain-derived neurotrophic factor, glutamate), endocannabinoid system, and serotonin system activation. Clinical studies have demonstrated that acupuncture may be a beneficial migraine treatment, particularly in decreasing pain intensity, duration, emotional comorbidity, and days of acute medication intake. However, specific clinical effectiveness has not been substantiated, and the mechanisms underlying its efficacy remain obscure. With the development of biomedical and neuroimaging techniques, the neural mechanism of acupuncture in migraine has gained increasing attention. Neuroimaging studies have indicated that acupuncture may alter the abnormal functional activity and connectivity of the descending pain modulatory system, default mode network, thalamus, frontal-parietal network, occipital-temporal network, and cerebellum. Acupuncture may reduce neuroinflammation, regulate peripheral and central sensitization, and normalize abnormal brain activity, thereby preventing pain signal transmission. To summarize the effects and neural mechanisms of acupuncture in migraine, we performed a systematic review of literature about migraine and acupuncture. We summarized the characteristics of current clinical studies, including the types of participants, study designs, and clinical outcomes. The published findings from basic neuroimaging studies support the hypothesis that acupuncture alters abnormal neuroplasticity and brain activity. The benefits of acupuncture require further investigation through basic and clinical studies.

Myocardial infarction associated with erenumab: A case report

Background

Monoclonal antibodies acting on the calcitonin gene‐related peptide or its receptor (CGRP‐mabs) are novel drugs for resistant migraine prophylaxis. As CGRP‐mabs cause inhibition of vasodilatation, their use is reserved to patients with no recent history of cardiovascular diseases. We report a case of myocardial infarction associated with erenumab.

Case

A 57‐year‐old woman with a familial history of coronaropathy was first treated with erenumab 70 mg for 6 months and then increased to 140 mg. Almost 5 months after, the patient presented chest pain, increased troponin, and abnormal electrocardiogram. A myocardial infarction without coronarography abnormality was diagnosed through MRI.

Conclusion

Further evidence is needed to assess the risk of myocardial infarction in patients treated with a CGRP‐mab. In patients over 40 years of age, the risk of coronary or cardiovascular events should be assessed using risk tables or algorithms to take into account cardiovascular risk factors. This may be complemented by appropriate examinations to measure the burden of coronary atherosclerosis, if necessary.

The Effects of Intervening With Synonasal Changes on Headaches in Migraine Patients Using Endonasal Surgery

OBJECTIVE

Some anatomical changes might trigger headaches in people who have migraine, and that surgical applications eliminating the structural problems in treatment-resistant migraine patients are effective in pain treatment.

METHODS

A total of 36 patients, who did not respond to different treatment options without aura migraine and chronic migraine that were showing synonasal and anatomical changes in synonasal nasal endoscopy and/or paranasal sinus CT screening, responding insufficiently and/or approximately one year period also did not respond to different treatment options, were included in this study between June 2016 and September 2019.

RESULTS

The relation between migraine episodes and synonasal symptoms was found to be statistically significant. A significant difference was detected between nasal congestion and obstruction, postnasal discharge, and runny nose in patients with attacks compared to patients without attacks. The difference between mean pain severity values was statistically significant when compared to preoperative values (3.0(3.0∼4.0)) and post-operative values (1.0(0∼1.0)). When the pain severity after the operation (1.0(1.0∼2.75)) was compared with the severity of pain before the operation (5.0 (3.0∼5.0)), it was determined that there was a significant decrease in pain severity in patients diagnosed with chronic migraine, the difference between the mean pain severity values was statistically significant, and the prevalence of pain decreased at a significant level after the operation.

CONCLUSION

The results of the present study indicate that the elimination of synonasal structural changes, which were hypothesized to trigger pain in migraine patients, could have a pain-reducing effect on the frequency and severity of the pain.

The neurobiology of cluster headache

Cluster headache is a primary headache form occurring in paroxysmal excruciatingly severe unilateral head pain attacks usually grouped in periods lasting 1-2months, the cluster periods. A genetic component is suggested by the familial occurrence of the disease but a genetic linkage is yet to be identified. Contemporary activation of trigeminal and cranial parasympathetic systems-the so-called trigemino-parasympathetic reflex-during the headache attacks seem to cause the pain and accompanying oculo-facial autonomic phenomena respectively. At peripheral level, the increased calcitonin gene related peptide (CGRP) plasma levels suggests trigeminal system activation during cluster headache attacks. The temporal pattern of the disease both in terms of circadian rhythmicity and seasonal recurrence has suggested involvement of the hypothalamic biological clock in the pathophysiology of cluster headache. The posterior hypothalamus was investigate as the cluster generator leading to activation of the trigemino-parasympathetic reflex, but the accumulated experience after 20 years of hypothalamic electrical stimulation to treat the condition indicate that this brain region rather acts as pain modulator. Efficacy of monoclonal antibodies to treat episodic cluster headache points to a key role of CGRP in the pathophysiology of the condition.

The Association Between Blood Pressure and Headache in Postmenopausal Women: A Prospective Hospital-Based Study

Background

Headache is the most frequent condition for outpatient patients because of neurological problems, but little is known about predisposing and enabling factors for headache patients.

Aim

To investigate the association between blood pressure (BP) and headache in postmenopausal women.

Methods

The postmenopausal women who were admitted to our hospital from January 2015 to December 2019 were screening according to the criteria. Their systolic BP (SBP), diastolic BP (DBP), pulse pressure (PP) were assessed and the information of age, body mass index, smoking status, caffeine consumption, cholesterol levels, and daily alcohol use were collected. Multiple logistic regression model was established to evaluate the association between BP and headache.

Results

A total of 1571 postmenopausal women were included in the analysis, including 953 headache-free population and 618 headache participants during the studied periods. We found that increasing SBP and PP were associated with the lower occurrence of migraine, tension-type headache (TTH), probable migraine, and unclassified headache (P < 0.05). However, there was a negative association between DBP levels and the new occurrence of overall headache, but we did not find any relations of DBP with any subtypes of headache.

Conclusion

There were negative associations of SBP and PP with new occurrence of headache, especially migraine and TTH, but there is no relationship between DBP and the subsequent development of headache.

Functional and structural alterations in the migraine cerebellum

The cerebellum plays an important role in pain processing but its function in headache and specifically in migraine is not known. We therefore compared 54 migraineurs with pairwise matched healthy controls in a magnetic resonance imaging study on neuronal cerebellar activity in response to nociceptive trigeminal sensation and also investigated possible structural alterations. Headache frequency, disease duration, and the proximity to a migraine attack were used as co-factors. Migraine patients showed functional and structural alterations in the posterior part of the cerebellum, namely crus I and crus II. Gray matter volume changes were seen on the right side whereas functional changes were ipsilateral to the stimulation, on the left side. Neuronal activity in the crus in response to trigeminal pain was modulated by migraine severity and the migraine phase. As the crus is strongly interconnected to higher cognitive areas in the temporal, frontal, and parietal part of the cortex our results suggest an specific cerebellar involvement in migraine. This is further supported by our finding of decreased connectivity from the crus to the thalamus and higher cortical areas in the patients. We therefore suggest an abnormally decreased inhibitory involvement of the migraine cerebellum on gating and nociceptive evaluation.

Neurovascular mechanisms of migraine and cluster headache

Vascular theories of migraine and cluster headache have dominated for many years the pathobiological concept of these disorders. This view is supported by observations that trigeminal activation induces a vascular response and that several vasodilating molecules trigger acute attacks of migraine and cluster headache in susceptible individuals. Over the past 30 years, this rationale has been questioned as it became clear that the actions of some of these molecules, in particular, calcitonin gene-related peptide and pituitary adenylate cyclase-activating peptide, extend far beyond the vasoactive effects, as they possess the ability to modulate nociceptive neuronal activity in several key regions of the trigeminovascular system. These findings have shifted our understanding of these disorders to a primarily neuronal origin with the vascular manifestations being the consequence rather than the origin of trigeminal activation. Nevertheless, the neurovascular component, or coupling, seems to be far more complex than initially thought, being involved in several accompanying features. The review will discuss in detail the anatomical basis and the functional role of the neurovascular mechanisms relevant to migraine and cluster headache.

Association of Gastrointestinal Functional Disorders and Migraine Headache: a Population Base Study

BACKGROUND Migraine is one of the prevalent headaches. Many of patients with migraine, complain of gastrointestinal symptoms. There is limited studies on relation of gastrointestinal symptoms and migraine headache at population level. METHODS In this population-based study, 1038 subjects older than 15 year from a rural area in Fars province, south of Iran. were investigated for functional gastrointestinal disorders. By cluster random sampling, 160 of these persons invited to receive endoscopy along with histopathology samples of upper gastrointestinal tract. Data were analyzed using Pearson chi-square and Fisher exact. RESULTS Mean age of participations were 34.3 years with female to male of 3:1. The prevalence of migraine, irritable bowel syndrome (IBS), reflux, and dyspepsia were 24.6%, 17.7%, 17.4%, and 32.1%, respectively. There were significant relationship between migraine and functional gastrointestinal diseases (odds ratio of association for migraine with IBS, reflux, and dyspepsia were 3.43, 1.68, and 1.68 with p-value < 0.001 for all). In endoscopic findings, only presence of hiatal hernia was associated significantly with migraine (p = 0.011). No histopathologic findings in antral or duodenal biopsies were associated with migraine. CONCLUSION In this population based study we found significant association between migraines and gastrointestinal functional disorders including IBS, reflux and dyspepsia. This may have implication in better management of patients with migraine headache.

Asymmetric Synthesis of the Major Metabolite of a Calcitonin Gene-Related Peptide Receptor Antagonist and Mechanism of Epoxide Hydrogenolysis

An asymmetric synthesis of the major metabolite of the calcitonin gene-related peptide recepotor antagonist BMS-846372 is presented. The variously substituted cyclohepta[b]pyridine ring system represents an underexplored ring system and showed some unexpected chemistry. Reactivities of epoxide and ketone functional groups on the cycloheptane ring were extensively controlled by a remote bulky TIPS group. The rate difference of the hydrogenolysis between two diastereomeric epoxide intermediates shed some light on the mechanism of epoxide hydrogenolysis, and further, deuterium labeling studies revealed more mechanistic details on this well-known chemical transformation for the first time.

A phase IIb randomized, double-blind, placebo-controlled trial of ubrogepant for the acute treatment of migraine

Aim

The aim of this trial was to evaluate the efficacy and tolerability of ubrogepant (MK-1602), a calcitonin gene-related peptide receptor antagonist (CGRP-RA), for the acute treatment of migraine.

Methods

This double-blind, placebo-controlled study randomized 834 participants to treat one migraine attack with ubrogepant 1 mg, 10 mg, 25 mg, 50 mg, 100 mg, or placebo in a 1:1 ratio. The co-primary endpoints were pain freedom and headache response at two hours. The first primary hypothesis tested the dose-response trend for two-hour pain freedom using a logistic regression model. Subsequent hypotheses tested the effects of each dose on the co-primary endpoints, using a closed sequential testing procedure to control for multiplicity.

Results

A total of 527 participants received ubrogepant and 113 received placebo. A positive response trend in the proportion of participants achieving two-hour pain freedom was demonstrated ( p < 0.001). Ubrogepant 100 mg was significantly superior to placebo for two-hour pain freedom (25.5% vs 8.9%) but not for two-hour headache response. Per the prespecified multiplicity strategy, this nonsignificant result precluded further formal hypothesis testing, although the 50 mg and 25 mg doses demonstrated nominal significance over placebo for two-hour pain freedom (unadjusted p < 0.05). Overall, adverse events were similar between ubrogepant and placebo.

Conclusion

This trial supports ubrogepant’s efficacy and provides further evidence that CGRP-RAs are viable options for the acute treatment of migraine.

Migraine Patients have Lower Systolic but Higher Diastolic Blood Pressure Compared with Controls in a Population-Based Study of 21 537 Subjects. The Reykjavik Study

Several studies have explored a possible association between migraine and hyper- tension, with contradictory results. Because of this uncertainty the relation between blood pressure (BP) and migraine was studied in 10 366 men and 11 171 women in a population-based longitudinal study. A modified version of the 1988 International Headache Society criteria was used for diagnosis of migraine. Logistic regression analysis was used. The crude 1-year prevalence of migraine was 5.2% among men and 14.1% among women. No significant association was found between hypertension and migraine. For a one standard deviation (SD) increase in diastolic BP the probability of having migraine increased 14% ( P = 0.11) for men and 30% ( P < 0.0001) for women. For a 1-SD increase in systolic BP the probability of having migraine decreased 19% ( P = 0.007) for men and 25% ( P < 0.0001) for women. It was also found that for a 1-SD increase in pulse pressure the probability of having migraine decreased 13% ( P = 0.005) for men and 14% ( P < 0.0001) for women. In a population-based study of men and women it was found that subjects with migraine had lower pulse pressure, lower systolic BP and higher diastolic BP compared with controls.

Evaluation of the changes in the nasal cavity during the migraine attack

OBJECTIVES

There are some subjective symptoms involving the nasal cavity such as nasal congestion during a migraine attack. In this study, we aimed to evaluate the possible changes occurring in the nasal cavity during headache in patients with migraine.

MATERIALS AND METHODS

Patients with migraine were studied. The control group consisted of patients with tension-type headache. The severity of the headache and accompanying complaints were assessed using visual analog scale, and the nasal mucosa was assessed through anterior rhinoscopy and endoscopy. Resistance of the nasal cavity was evaluated through anterior rhinomanometry. Data obtained during the attack periods and attack-free periods were compared.

RESULTS

Twenty-five patients with migraine and 15 patients with tension-type headache were enrolled. It was found that 19 patients (76%) of the group with migraine and 5 patients of the group with tension-type headache were experiencing nasal congestion during the attack and that the differences between the groups were statistically significant (P < 0.05). The average of total nasal resistance in the patients with migraine was 0.57 ± 0.60 kPa/L/sn during migraine attacks and 0.28 ± 0.14 kPa/L/sn during attack-free periods. The average of total nasal resistance in the patients with tension-type headache was 0.32 ± 0.14 kPa/L/sn during attack periods and 0.31 ± 0.20 kPa/L/sn during attack-free periods. In the group with migraine, the change of nasal resistance between during the attack and attack-free periods was found statistically significant, whereas there was no statistically significant difference in the group with tension-type headache.

CONCLUSIONS

According to the results of this study, complaints regarding nasal obstruction and nasal airway resistance increase during migraine attacks. Cause-and-effect relationship between nasal obstruction and pain is not clear, and clinical trials are needed to determine the effect of nasal obstruction treatment (mucosal decongestion, etc) on the complaint of pain.

The Journey to Establish CGRP as a Migraine Target: A Retrospective View

In this retrospective, Dr. Lars Edvinsson recounts early steps and milestones in our understanding of the neuropeptide calcitonin gene-related peptide (CGRP) in the trigeminovascular system and its role in migraine. The discovery of the presence and function of CGRP and other neuropeptides in the cerebral vasculature and its sensory innervation is described. He relates the seminal finding that CGRP is uniquely released during migraine and the journey to develop blockers of CGRP effects. Now, over 30 years since its discovery, CGRP has become the target for a number of promising novel treatments for migraine patients.

Targeting CGRP: A New Era for Migraine Treatment

Migraine is a highly prevalent headache disease that typically affects patients during their most productive years. Despite significant progress in understanding the underlying pathophysiology of this disorder, its treatment so far continues to depend on drugs that, in their majority, were not specifically designed for this purpose. The neuropeptide calcitonin gene-related peptide (CGRP) has been indicated as playing a critical role in the central and peripheral pathways leading to a migraine attack. It is not surprising that drugs designed to specifically block its action are gaining remarkable attention from researchers in the field with, at least so far, a safe risk profile. In this article, we highlight the evolution from older traditional treatments to the innovative CGRP target drugs that are revolutionizing the way to approach this debilitating neurological disease. We provide a brief introduction on pathophysiology of migraine and details on the characteristic, function, and localization of CGRP to then focus on CGRP receptor antagonists (CGRP-RAs) and CGRP monoclonal antibodies (CGRP mAbs).

Preparation of imidazoles as potent calcitonin gene-related peptide (CGRP) antagonists

Several new potent CGRP receptor antagonists have been prepared in which the amide bond of lead compound 1 has been replaced by bioisosteric imidazole moieties. Substitution at N-1 of the imidazole was optimized to afford compounds with comparable potency to that of lead 1. Conformational restraint of the imidazole to form tetrahydroimidazo[1,5-a]pyrazine 43 gave substantially improved permeability.

Lack of hemodynamic interaction between CGRP-receptor antagonist telcagepant (MK-0974) and sumatriptan: results from a randomized study in patients with migraine

OBJECTIVE

The objective of this article is to assess the effects of sumatriptan monotherapy, telcagepant monotherapy, and their combination on blood pressure (BP) in migraine patients during a headache-free period.

METHODS

A double-blind, placebo-controlled, four-period, single-dose, randomized crossover study in 24 migraine patients was conducted. In each period, patients received a single oral dose of sumatriptan 100 mg alone, telcagepant 600 mg alone, sumatriptan 100 mg coadministered with telcagepant 600 mg, or placebo. Semi-recumbent BP was measured pre-dose and at seven post-dose time points over a period of six hours. Individual time-weighted averages in mean arterial pressure (MAP) were evaluated using a linear mixed-effects model. The pharmacokinetics of sumatriptan alone and in the presence of telcagepant were also evaluated using limited sampling times.

RESULTS

The mean difference in time-weighted (0-2.5 h) MAP (90% confidence interval) was 1.2 mmHg (-0.2, 2.7) between telcagepant and placebo, 4.0 mmHg (2.5, 5.5) between sumatriptan and placebo, and 1.5 mmHg (0.0, 3.0) between telcagepant with sumatriptan vs sumatriptan alone. When coadministered with telcagepant, the AUC0-6h and C(max) of sumatriptan were increased by 23% and 24%, respectively. The small MAP increases observed after coadministration could possibly be associated with the slight elevations in sumatriptan levels.

CONCLUSION

Telcagepant does not elevate mean MAP, and coadministration of telcagepant with sumatriptan results in elevations in MAP similar to those observed following administration of sumatriptan alone in migraineurs during the interictal period. When coadministered, telcagepant slightly increases the plasma levels of sumatriptan, but without an apparent clinically meaningful effect.

Pearls and pitfalls in neural CGRP immunohistochemistry

This review outlines the pearls and pitfalls of calcitonin-gene related protein (CGRP) immunohistochemistry of the brain.

Pearls

In 1985, CGRP was first described in cerebral arteries using immunohistochemistry. Since then, cerebral CGRP (and, using novel antibodies, its receptor components) has been widely scrutinized. Here, we describe the distribution of cerebral CGRP and pay special attention to the surprising reliability of results over time.

Pitfalls

Pitfalls might include a fixation procedure, antibody clone and dilution, and interpretation of results. Standardization of staining protocols and true quantitative methods are lacking. The use of computerized image analysis has led us to believe that our examination is objective. However, in the steps of performing such an analysis, we make subjective choices. By pointing out these pitfalls, we aim to further improve immunohistochemical quality.

Recommendations

Having a clear picture of the tissue/cell morphology is a necessity. A primary morphological evaluation with, for example, hematoxylin-eosin, helps to ensure that small changes are not missed and that background and artifactual changes, which may include vacuoles, pigments, and dark neurons, are not over-interpreted as compound-related changes. The antigen-antibody reaction appears simple and clear in theory, but many steps might go wrong. Remember that methods including the antigen-antibody complex rely on handling/fixation of tissues or cells, antibody shipping/storing issues, antibody titration, temperature/duration of antibody incubation, visualization of the antibody and interpretation of the results. Optimize staining protocols to the material you are using.

Discovery of (5S,6S,9R)-5-amino-6-(2,3-difluorophenyl)-6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridin-9-yl 4-(2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-1-yl)piperidine-1-carboxylate (BMS-927711): an oral calcitonin gene-related peptide (CGRP) antagonist in clinical trials for treating migraine

Calcitonin gene-related peptide (CGRP) receptor antagonists have demonstrated clinical efficacy in the treatment of acute migraine. Herein, we describe the design, synthesis, and preclinical characterization of a highly potent, oral CGRP receptor antagonist BMS-927711 (8). Compound 8 has good oral bioavailability in rat and cynomolgus monkey, attractive overall preclinical properties, and shows dose-dependent activity in a primate model of CGRP-induced facial blood flow. Compound 8 is presently in phase II clinical trials.

Discovery of BMS-846372, a Potent and Orally Active Human CGRP Receptor Antagonist for the Treatment of Migraine

Calcitonin gene-related peptide (CGRP) receptor antagonists have been clinically shown to be effective in the treatment of migraine, but identification of potent and orally bioavailable compounds has been challenging. Herein, we describe the conceptualization, synthesis, and preclinical characterization of a potent, orally active CGRP receptor antagonist 5 (BMS-846372). Compound 5 has good oral bioavailability in rat, dog, and cynomolgus monkeys and overall attractive preclinical properties including strong (>50% inhibition) exposure-dependent in vivo efficacy in a marmoset migraine model.

Neurovascular compression of the greater occipital nerve: implications for migraine headaches

BACKGROUND

Surgical release of the greater occipital nerve has been demonstrated to be clinically effective in eliminating or reducing chronic migraine symptoms. However, migraine symptoms in some patients continue after this procedure. It was theorized that a different relationship between the greater occipital nerve and occipital artery may exist in these patients that may be contributing to these outcomes. A cadaveric investigation was performed in an effort to further delineate the occipital artery-greater occipital nerve relationship.

METHODS

Fifty sides of 25 fresh cadaveric posterior necks and scalps were dissected. The greater occipital nerve was identified within the subcutaneous tissue and its relationship with the occipital artery was delineated. A topographic map of the intersection of the two structures was created.

RESULTS

The greater occipital nerve and occipital artery have an intimate relationship, and crossed each other in 27 hemiheads (54.0 percent). The relationship between these structures when they crossed varied from a single intersection to a helical intertwining.

CONCLUSIONS

The greater occipital nerve and occipital artery have an anatomical intersection 54 percent of the time. There are two morphologic types of relationships between the structures: a single intersection point and a helical intertwining. Vascular pulsation may cause irritation of the nerve and is a possible explanation for migraine headaches that have the occipital region as a trigger point. Future imaging studies and clinical investigation is necessary to further examine the link between anatomy and clinical presentation.

Cerebellar distribution of calcitonin gene-related peptide (CGRP) and its receptor components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) in rat

Clinical and experimental results have revealed a fundamental role of calcitonin gene-related peptide (CGRP) in primary headaches. CGRP is widely expressed in neurons both in the central nervous system (CNS) and in peripheral sensory nerves. In the CNS there is a wide distribution of CGRP-containing neurons with the highest levels seen in striatum, amygdale and cerebellum. Moreover, in acute attacks of migraine there is evidence of cerebellar activation. To understand the role of CGRP, antibodies towards the CGRP receptor components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein type 1 (RAMP1) have been developed. In the present study we therefore examined immunohistochemically the distribution of CGRP and its receptor components in the cerebellum. CGRP immunoreactivity was only found intracellularly in the cerebellar Purkinje cell bodies, whereas CLR and RAMP1 were detected on the surface of the Purkinje cell bodies and in their processes. The elaborate dendritic tree of Purkinje cell fibers was distinctly visualized with the RAMP1 antibody. In addition, profoundly stained fibers spanning from the molecular layer into the medulla was observed with the RAMP1 antibody. Judged from the high density of immunoreactive cells expressing CGRP, RAMP1 or CLR, and from the double staining of CGRP and RAMP1 it is likely that most, if not all, Purkinje cells express both the peptide and the receptor components. Double staining with RAMP1 and the glial cell markers glial fibrillary acidic protein (GFAP) and S-100 revealed an almost identical staining pattern of the antibodies in the area of the cell body surfaces. However, as judged by confocal microscopy, no double staining was present. Instead, it was discovered that the glial cells tightly surrounded the Purkinje cells which easily could be interpreted as co-localization in the epifluorescence microscope. Our observations demonstrate that there is a rich expression of CGRP and CGRP receptor elements in the cerebellum which points towards a functional role of CGRP in cerebellar Purkinje cells. Recent advances in the biology of the cerebellum indicate that there may be a role in nociception; hence a target of the recently discovered CGRP receptor antagonists that have demonstrated improvement in migraine pain and associated symptoms could be cerebellar CGRP receptors.

Asymmetric synthesis of telcagepant, a CGRP receptor antagonist for the treatment of migraine

A highly efficient, asymmetric synthesis of telcagepant (1), a CGRP receptor antagonist for the treatment of migraine, is described. This synthesis features the first application of iminium organocatalysis on an industrial scale. The key to the success of this organocatalytic transformation was the identification of a dual acid cocatalyst system, which allowed striking a balance of the reaction efficiency and product stability effectively. As such, via an iminium species, the necessnary C-6 stereogenicity was practically established in one operation in >95% ee. Furthermore, we enlisted an unprecedented Doebner-Knoevenagel coupling, which was also via an iminium species, to efficiently construct the C3-C4 bond with desired functionality. In order to prepare telcagepant (1) in high quality, a practical new protocol was discovered to suppress the formation of desfluoro impurities formed under hydrogenation conditions to <0.2%. An efficient lactamization facilitated by t-BuCOCl followed by a dynamic epimerization-crystallization resulted in the isolation of caprolactam acetamide with the desired C3 (R) and C6 (S) configuration cleanly. Isolating only three intermediates, the overall yield of this cost-effective synthesis was up to 27%. This environmentally responsible synthesis contains all of the elements required for a manufacturing process and prepares telcagepant (1) with the high quality required for pharmaceutical use.

Organ culture of the trigeminal ganglion induces enhanced expression of calcitonin gene-related peptide via activation of extracellular signal-regulated protein kinase 1/2

BACKGROUND AND OBJECTIVE

Clinical and experimental studies have revealed a central role of calcitonin gene-related peptide (CGRP) in primary headaches. The role of extracellular signal-regulated kinase 1 and 2 (ERK1/2) in neuronal and glial cell expression of CGRP- immunoreactivity (-ir) in rat trigeminal ganglia was studied with an organ culture method.

EXPERIMENTAL PROCEDURES

Sections of adult rat trigeminal ganglia were cultured for up to 48 hours, examined with immunohistochemistry and quantitative real-time polymerase chain reaction (PCR) assay. Specific antibodies against CGRP, phosphorylated ERK1/2 (pERK1/2), total ERK1/2 (tERK1/2), phosphorylated p38 (pp38), phosphorylated C-Jun-N-terminal protein kinase (pJNK), pro-calcitonin (pro-CT), CGRP receptor activity modifying protein 1 (RAMP1), glutamine synthetase (GS) and pro-CT were used. To explore molecular mechanisms involved in the organ culture-induced CGRP-ir in neurons and glial cells, the effects of the MEK/ERK1/2 inhibitor U0126, its inactive analogue U0124, the p38 inhibitor SB203580 and the JNK inhibitor SP600125 were studied.

RESULTS

In fresh ganglia, small- and medium-sized neurons were CGRP-ir while some larger neurons displayed RAMP1-ir. Glial cells were negative to both. After organ culture, neurons showed enhanced CGRP- and RAMP1-ir. In addition, some glial cells were RAMP1- and CGRP-ir. Isolated glial cells and neurons were found to contain CGRP mRNA, and showed pro-CT-ir, suggestive of local formation of CGRP. Neurons and glial cells showed enhanced pERK1/2-ir already after two hours of organ culture and this remained elevated for 48 hours. There was transient pJNK-ir in neurons at two hours, while pp38-ir was not altered. U0126 reduced the enhanced pERK1/2-ir, while U0124 had no such effect; the CGRP-ir in neurons and glial cells was reduced at 48 hours and in parallel the CGRP mRNA expression was lower at 24 hours.

CONCLUSION

We suggest that in conditions of elevated CGRP expression, inhibition of ERK1/2 might be an option for novel treatment.

BDNF and CGRP interaction: Implications in migraine susceptibility

Objectives: Migraine pathophysiology involves several pathways. Our aims were to explore a possible role of the brain-derived neurotrophic factor gene ( BDNF) in migraine susceptibility; to study, for the first time, the calcitonin gene-related peptide gene ( CGRP); and a possible interaction between the two.

Methods: Using a case-control approach, four tagging single nucleotide polymorphisms (SNPs) (rs7124442, rs6265, rs11030107, and rs2049046) of BDNF and one tagging SNP—rs1553005—of CGRP were analyzed in 188 cases and 287 controls. A multivariable logistic regression was performed, adjusting for gender. Allelic and haplotypic frequencies were estimated. Interaction was assessed by a stepwise multivariable-logistic regression and confirmed by a multifactor dimensionality reduction analysis.

Results: No significant main effects were found; however, a significant interaction was found between BDNF and CGRP, showing an increased risk for the AT-genotype of rs2049046 and the GC-genotype of rs1553005 (odds ratio = 1.88, 95% confidence interval: 1.20–2.93) for migraineurs.

Conclusion: Our data support the hypothesis of an interaction between BDNF and CGRP in migraine susceptibility that should be further explored.

CGRP receptor antagonism and migraine

Calcitonin gene-related peptide (CGRP) is expressed throughout the central and peripheral nervous systems, consistent with control of vasodilatation, nociception, motor function, secretion, and olfaction. alphaCGRP is prominently localized in primary spinal afferent C and ADelta fibers of sensory ganglia, and betaCGRP is the main isoform in the enteric nervous system. In the CNS there is a wide distribution of CGRP-containing neurons, with the highest levels occurring in striatum, amygdala, colliculi, and cerebellum. The peripheral projections are involved in neurogenic vasodilatation and inflammation, and central release induces hyperalgesia. CGRP is released from trigeminal nerves in migraine. Trigeminal nerve activation results in antidromic release of CGRP to cause non-endothelium-mediated vasodilatation. At the central synapses in the trigeminal nucleus caudalis, CGRP acts postjunctionally on second-order neurons to transmit pain signals centrally via the brainstem and midbrain to the thalamus and higher cortical pain regions. Recently developed CGRP receptor antagonists are effective at aborting acute migraine attacks. They may act both centrally and peripherally to attenuate signaling within the trigeminovascular pathway.

Evidence-based interventional pain medicine according to clinical diagnoses. 2. Cluster headache

Cluster headache is a strictly unilateral headache that is associated with ipsilateral cranial autonomic symptoms and usually has a circadian and circannual pattern. Prevalence is estimated at 0.5 to 1.0/1,000. The diagnosis of cluster headache is made based on the patient's case history. There are two main clinical patterns of cluster headache: the episodic and the chronic. Episodic is the most common pattern of cluster headache. It occurs in periods lasting 7 days to 1 year and is separated by at least a 1-month pain-free interval. The attacks in the chronic form occur for more than 1 year without remission periods or with remission periods lasting less than 1 month. Conservative therapy consists of abortive and preventative remedies. Ergotamines and sumatriptan injections, sublingual ergotamine tartrate administration, and oxygen inhalation are effective abortive therapies. Verapamil is an effective and the safest prophylactic remedy. When pharmacological and oxygen therapies fail, interventional pain treatment may be considered. The effectiveness of radiofrequency treatment of the ganglion pterygopalatinum and of occipital nerve stimulation is only evaluated in observational studies, resulting in a 2 C+ recommendation. In conclusion, the primary treatment is medication. Radiofrequency treatment of the ganglion pterygopalatinum should be considered in patients who are resistant to conservative pain therapy. In patients with cluster headache refractory to all other treatments, occipital nerve stimulation may be considered, preferably within the context of a clinical study.

Glyceroltrinitrate facilitates stimulated CGRP release but not gene expression of CGRP or its receptor components in rat trigeminal ganglia

Nitric oxide (NO) donors induce delayed headaches in migraineurs. In a corresponding rat model NO donors cause delayed ongoing activity in central trigeminal neurons which process intracranial afferent input. Cellular models indicate that NO may increase the release or production of calcitonin gene-related peptide (CGRP), a key mediator in primary headaches. CGRP release from intact isolated trigeminal ganglia of adult male Wistar rats was investigated in vitro. Exposure to high NO donor concentrations did not affect basal or stimulated CGRP release. After a two hour infusion of the NO donor glyceroltrinitrate (250microg/kg/h), however, inflammatory mediators-induced CGRP release was 80% higher compared to control animals. Administration of the soluble guanylate cyclase inhibitor ODQ or the application of 8Br-cGMP revealed a cGMP-independent mechanism. In four groups of separate experiments total mRNA was extracted from rat trigeminal ganglia up to 6h after glyceroltrinitrate or saline infusion. Gene expression of CGRP and the CGRP-receptor components, receptor activity-modifying protein 1, receptor component protein and calcitonin receptor-like receptor was measured by quantitative RT-PCR. Glyceroltrinitrate infusion did not change mRNA levels of these genes compared to infusion of saline. The present data suggest that prolonged increase in NO levels facilitates stimulated CGRP release from trigeminal ganglion neurons. The underlying mechanism appears to be independent of the cGMP pathway and not to interact with CGRP in the trigeminal ganglion. Delayed headaches induced by NO may change CGRP or CGRP-receptor expression.

Calcitonin gene-related peptide (CGRP) levels during glyceryl trinitrate (GTN)-induced headache in healthy volunteers

The role of nitric oxide (NO) in migraine has been studied in the experimental glyceryl trinitrate (GTN)-infusion headache model. We hypothesized that GTN-induced headache may activate the trigeminovascular system and be associated with increased levels of sensory neuropeptides, including calcitonin gene-related peptide (CGRP). CGRP, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and somatostatin plasma levels were measured before and after placebo/sumatriptan injection and during GTN-induced headache. Following a double-blind randomized cross-over design, 10 healthy volunteers received subcutaneous sumatriptan 6 mg or placebo. This was succeeded by 20 min of GTN (0.12 µg kg−1 min−1) infusion. At baseline no subject reported headache (using verbal rating scale from 0 to 10) and the jugular CGRP-like immunoreactivity (-LI) level was 18.6 ± 2.5 pmol/l. After a 20-min intravenous infusion of GTN 0.12 µg kg−1 min−1, median peak headache intensity was 4 (range 2–6) ( P < 0.05), while jugular CGRP-LI levels were unchanged (19.0 ± 2.8 pmol/l; P > 0.05). There were no changes in VIP-, NPY- or somatostatin-LI. In conclusion, the NO donor GTN appears not to induce headache via immediate CGRP release.

Effect of central serotonin depletion on 5-HT receptor-mediated vasomotor responses in the middle meningeal artery of anaesthetized rats

1 It has been hypothesized that craniovascular 5-HT receptors mediating dilatation of cranial vessels undergo sensitization on decreased serotonergic transmission in migraine. This study analysed the effect of chemical lesion of the 5-HT system in the brain with 5,7-dihydroxytryptamine (5,7-DHT) on 5-HT receptor-mediated dilator responses to 5-carboxamidotryptamine (5-CT) in the middle meningeal artery of anaesthetized rats. 5-CT has recently been shown to elicit dilator responses in this cranial vessel via 5-HT(7) receptors and, to a much lesser extent, 5-HT(1B/1D) receptors. 2 Pretreatment with 5,7-DHT produced a drastic and selective decrease of 5-HT levels in the brain (78 +/- 6% and 94 +/- 2% in dorsal raphe and hypothalamic paraventricular nuclei, respectively) compared with controls (1% ascorbic acid). 3 Topical application of 5-CT (1-1000 microm) to exposed dura mater encephali produced concentration-dependent decreases in diastolic blood pressure and dilator responses in the middle meningeal artery that were similar in vehicle- and 5,7-DHT-pretreaed animals. 4 Hypotensive and meningeal dilator responses to 5-CT were unaltered by the 5-HT(1B/1D) receptor antagonist, GR-127935 (1 mg kg(-1), i.v.), but were strongly inhibited by the 5-HT(7) receptor antagonist, SB-269970 (1 mg kg(-1), i.v.), with similar efficacy, in both groups of animals. Treatment with GR-127935 + SB-269970 (1 mg kg(-1), i.v. each), produced a stronger inhibitory effect than individual treatments on hypotensive but not on meningeal responses to 5-CT. Meningeal 5-HT(7) receptor-mediated responses (i.e. in GR-127935-pretreated animals) were unchanged by 5,7-DHT pretreatment. 5 Results suggest that the sensitivity of craniovascular 5-HT(7) receptors mediating dilatation is unaffected by a decrease of 5-HT levels in the brain. A neuronal involvement of 5-HT in migraine seems more likely, therefore.

Migraine pain: reflections against vasodilatation

The original Wolff’s vascular theory of migraine was supported by the discovery of a class of drugs, the triptans, developed as a selective cephalic vasoconstrictor agents. Even in the neurovascular hypothesis of Moskowitz, that is the neurogenic inflammation of meningeal vessels provoked by peptides released from trigeminal sensory neurons, the vasodilatation provoked by calcitonin gene-related peptide (CGRP) is considered today much more important than oedema. The role of cephalic vasodilatation as a cause of migraine pain was recently sustained by studies showing the therapeutic effect of CGRP receptor antagonists. We discuss the evidence against vasodilatation as migraine pain generator and some findings which we suggest in support of a central (brain) origin of pain.