Involvement of 5-HT1B and 5-HT1D receptors in sumatriptan mediated vasocontractile response in rabbit common carotid artery

Voltage-gated Calcium Channels as Potential Therapeutic Targets in Migraine

Migraine is a complex and highly incapacitating neurological disorder that affects around 15% of the general population with greater incidence in women, often at the most productive age of life. Migraine physiopathology is still not fully understood, but it involves multiple mediators and events in the trigeminovascular system and the central nervous system. The identification of calcitonin gene-related peptide as a key mediator in migraine physiopathology has led to the development of effective and highly selective antimigraine therapies. However, this treatment is neither accessible nor effective for all migraine sufferers. Thus, a better understanding of migraine mechanisms and the identification of potential targets are still clearly warranted. Voltage-gated calcium channels (VGCCs) are widely distributed in the trigeminovascular system, and there is accumulating evidence of their contribution to the mechanisms associated with headache pain. Several drugs used in migraine abortive or prophylactic treatment target VGCCs, which probably contributes to their analgesic effect. This review aims to summarize the current evidence of VGGC contribution to migraine physiopathology and to discuss how current pharmacological options for migraine treatment interfere with VGGC function. PERSPECTIVE: Calcitonin gene-related peptide (CGRP) represents a major migraine mediator, but few studies have investigated the relationship between CGRP and VGCCs. CGRP release is calcium channel-dependent and VGGCs are key players in familial migraine. Further studies are needed to determine whether VGCCs are suitable molecular targets for treating migraine.

Screening for Serotonin Receptor 4 Agonists Using a GPCR-Based Sensor in Yeast

More than 30% of all pharmaceuticals target G-protein-coupled receptors (GPCRs). Here, we present a GPCR-based screen in yeast to identify ligands for human serotonin receptor 4 (5-HTR₄). Serotonin receptor 4 agonists are used for the treatment of irritable bowel syndrome with constipation. Specifically, the HTR₄-based screen couples activation of 5-HTR₄ on the yeast cell surface to luciferase reporter expression. The HTR₄-based screen has a throughput of one compound per second allowing the screening of more than a thousand compounds per day.

Side effects associated with current and prospective antimigraine pharmacotherapies

INTRODUCTION

Migraine is a neurovascular disorder. Current acute specific antimigraine pharmacotherapies target trigeminovascular 5-HT1B/1D, 5-HT1F and CGRP receptors but, unfortunately, they induce some cardiovascular and central side effects that lead to poor treatment adherence/compliance. Therefore, new antimigraine drugs are being explored. Areas covered: This review considers the adverse (or potential) side effects produced by current and prospective antimigraine drugs, including medication overuse headache (MOH) produced by ergots and triptans, the side effects observed in clinical trials for the new gepants and CGRP antibodies, and a section discussing the potential effects resulting from disruption of the cardiovascular CGRPergic neurotransmission. Expert opinion: The last decades have witnessed remarkable developments in antimigraine therapy, which includes acute (e.g. triptans) and prophylactic (e.g. β-adrenoceptor blockers) antimigraine drugs. Indeed, the triptans represent a considerable advance, but their side effects (including nausea, dizziness and coronary vasoconstriction) preclude some patients from using triptans. This has led to the development of the ditans (5-HT1F receptor agonists), the gepants (CGRP receptor antagonists) and the monoclonal antibodies against CGRP or its receptor. The latter drugs represent a new hope in the antimigraine armamentarium, but as CGRP plays a role in cardiovascular homeostasis, the potential for adverse cardiovascular side effects remains latent.

Functional serotonin and histamine receptor subtypes in porcine ciliary artery in comparison with middle cerebral artery

Functional serotonin (5-HT) and histamine receptor subtypes were investigated in porcine middle cerebral and ciliary arteries. An H(1) antagonist, mepyramine, antagonized histamine-induced responses with pK(B) values of 8.91-9.10. In the presence of 1 muM mepyramine, however, histamine caused dilation through H(2) receptors in the middle cerebral but not in the ciliary artery. A 5-HT(2A) antagonist, ketanserin, antagonized 5-HT-induced responses, causing rightward shifts in the concentration-response curves with pK(B) values of 8.52-8.71. A 5-HT(1B) antagonist, SB224289, produced rightward shifts of the concentration-response curves to sumatriptan with pK(B) values (6.66) only in the middle cerebral artery. In contrast, a 5-HT(1D) antagonist, BRL15572, had no effect in either artery. An RT-PCR study demonstrated the gene expression of the mRNAs of all three receptors (5HT(1B), 5HT(1D) and 5HT(2A)) in both arteries. These results suggest that histamine-induced contraction is mediated only through functional H(1) receptor in these arteries. Interestingly, there are functional 5-HT(2A) and 5-HT(1B) receptor subtypes in the middle cerebral artery, whereas the only functional receptor is 5-HT(2A) in the ciliary artery. The difference may be important for treatment with 5-HT(1B/1D) agonists (e.g. for migraine) without ocular side effect.

Rat carotid artery responses to alpha-adrenergic receptor agonists and 5-HT after ovariectomy and hormone replacement

OBJECTIVE

To compare the contractile responses to alpha-adrenergic receptor agonists and 5-HT in the rat carotid artery after ovariectomy and subsequent hormone replacement with 17beta-estradiol, progesterone, or the combination of 17beta-estradiol and progesterone.

BACKGROUND

The prevalence of migraine is higher in women than in men, and changes in 17beta-estradiol levels seem to affect the frequency of attacks in female migraineurs. However, the underlying mechanisms are not yet completely understood.

METHODS

After 1 week of acclimatization (Day 0), female Sprague-Dawley rats were either sham-operated or bilateral ovariectomized. One week later (Day 7), the ovariectomized rats were subcutaneously implanted with a pellet releasing over a 21-day period either placebo, 0.25 mg 17beta-estradiol, 50 mg progesterone, or the combination of the 2 hormones. Blood samples were collected on Days 0, 7, and 21 to measure plasma norepinephrine and epinephrine. On days 25 to 28, the animals were killed to isolate carotid artery and mount its segments in Mulvany myographs. Cumulative concentration response curves to alpha-adrenergic receptor agonists and 5-HT were constructed in the absence or presence of suitable antagonists.

RESULTS

The potency of norepinephrine in ovariectomized rats was significantly reduced in animals treated with progesterone as compared to those with placebo. In placebo-treated ovariectomized animals there was a noticeable response mediated by alpha2-adrenoceptors, in contrast to that in sham-operated or ovariectomized rats treated with 17beta-estradiol and progesterone, either alone or in combination. The plasma levels of norepinephrine and epinephrine were not significantly affected by either ovariectomy or the subsequent hormone replacement. The potency of 5-HT was significantly reduced in animals having circulating sex hormones as compared to that in placebo-treated ovariectomized animals.

CONCLUSION

Taken together, our results indicate that circulating progesterone and/or 17beta-estradiol may reduce the contraction of the rat carotid artery in response to norepinephrine and 5-HT. This effect of female sex hormones might be one of the factors through which these hormones aggravate migraine in women.

G Protein β3 Polymorphism and Triptan Response in Cluster Headache

Only about 70% of migraine and cluster headache (CH) patients report significant treatment responses to triptans, which are agonists at 5-HT(1B/D) receptors belonging to the family of G protein-coupled receptors. We analyzed whether a common polymorphism in the gene for the G protein beta3 subunit (GNB3 C825T) modulates responder rates to triptans among a cohort of 231 unrelated Caucasian CH patients. A total of 180 CH patients used triptans, of whom 71.1% reported treatment success. The adjusted odds ratio for treatment response to triptans for heterozygous carriers of the GNB3 825T allele was 2.96 (95% confidence interval 1.34-6.56; P=0.0074) vs carriers of the 825CC genotype. The GNB3 genotype status did not affect responses to other acute and preventive therapeutic regimes including oxygen, verapamil, and corticosteroids, i.e., drugs not directly affecting G proteins. We conclude that pain relief by triptans is significantly modulated by a common genetic GNB3 variant.

Functions of 5-HT2A receptor and its antagonists in the cardiovascular system

The serotonin (5-hydroxytryptamine, 5-HT) receptors have conventionally been divided into seven subfamilies, most of which have several subtypes. Among them, 5-HT(2A) receptor is associated with the contraction of vascular smooth muscle, platelet aggregation and thrombus formation and coronary artery spasms. Accordingly, selective 5-HT(2A) antagonists may have potential in the treatment of cardiovascular diseases. Sarpogrelate, a selective 5-HT(2A) antagonist, has been introduced clinically as a therapeutic agent for the treatment of ischemic diseases associated with thrombosis. Molecular modeling studies also suggest that sarpogrelate is a 5-HT(2A) selective antagonist and is likely to have pharmacological effects beneficial in the treatment of cardiovascular diseases. This review describes the above findings as well as the signaling linkages of the 5-HT(2A) receptors and the mode of agonist binding to 5-HT(2A) receptor using data derived from molecular modeling and site-directed mutagenesis.