Receptor specificity and trigemino-vascular inhibitory actions of a novel 5-HT1B/1D receptor partial agonist, 311C90 (zolmitriptan)

Delineating a serotonin 1B receptor circuit for appetite suppression in mice

Triptans are a class of commonly prescribed antimigraine drugs. Here, we report a previously unrecognized role for them to suppress appetite in mice. In particular, frovatriptan treatment reduces food intake and body weight in diet-induced obese mice. Moreover, the anorectic effect depends on the serotonin (5-HT) 1B receptor (Htr1b). By ablating Htr1b in four different brain regions, we demonstrate that Htr1b engages in spatiotemporally segregated neural pathways to regulate postnatal growth and food intake. Moreover, Htr1b in AgRP neurons in the arcuate nucleus of the hypothalamus (ARH) contributes to the hypophagic effects of HTR1B agonists. To further study the anorexigenic Htr1b circuit, we generated Htr1b-Cre mice. We find that ARH Htr1b neurons bidirectionally regulate food intake in vivo. Furthermore, single-nucleus RNA sequencing analyses revealed that Htr1b marks a subset of AgRP neurons. Finally, we used an intersectional approach to specifically target these neurons (Htr1bAgRP neurons). We show that they regulate food intake, in part, through a Htr1bAgRP→PVH circuit.

Evaluation of Brain Targeting Potential of Zolmitriptan Mucoadhesive Nanoparticles for Intranasal Drug Delivery

BACKGROUND

Hydrophilic drugs are poor applicants of brain targeting via oral route due to the presence of blood-brain barrier that allows only small lipophilic molecules to freely access the brain. Due to unique anatomical connections between the nasal cavity and the brain, intranasal administration can be explored for drug delivery to the brain directly that circumvents blood-brain barrier too.

OBJECTIVES

Zolmitriptan is a widely used antimigraine drug and its brain targeting by nasal route in form of mucoadhesive nanoparticles is more effective in migraine treatment as it provide fast relief and good bioavailability as compared to its oral drug delivery. In the present study zolmitriptan mucoadhesive nanoparticles were prepared to improve the bioavailability and brain targeting for the better management of Migraine attacks.

METHODS

The mucoadhesive polymeric nanoparticles of zolmitriptan were formulated by modified ionic gelation method using thiolated chitosan. The pharmacokinetic parameters were counted in male Wistar rats by intranasal and oral delivery of anti-migraine drug zolmitriptan and compared statistically. The concentration of zolmitriptan in the blood plasma and brain samples was determined by using liquid-liquid extraction method followed by a reversed- phase high performance liquid chromatography (RP-HPLC) analysis. The pharmacodynamic analysis was done in adult male Swiss albino mice by behavioral models, light/dark box model, and acetic acid- induced writhing (abdominal stretching or constriction). These tests were used to reproduce the important associated symptoms of migraine viz. hyperalgesia (nociceptive sensitization) and photophobia for the assessment of the therapeutic potential of intranasal delivery of nanoparticles for anti-migraine activity.

RESULTS

The absolute bioavailability accessed for Zolmitriptan nanoparticles by IN route was found to be very high (193%), suggested that the sufficient amount drug transported by nanoparticles and DTE ratio was calculated 2.8, revealed better nose to brain transport by zolmitriptan nanoparticles as compared to oral delivery in male Wistar rats. A Significant increase in tolerance capacity of animals to bright light and fall in the numbers of stretching in mice suggested that the better management of migraine-associated symptoms by the zolmitriptan nanoparticles.

CONCLUSION

Thus present study confers the significance of nasal drug delivery for brain targeting of zolmitriptan nanoparticles for the treatment of migraine.

Preparation and characterization of immobilized 5-HT1A receptor stationary phase for high throughput screening of the receptor-binding ligands from complex systems like Curcuma wenyujin Y. H. Chen et C. Ling extract

The incidence of depression has increased significantly during the COVID-19 pandemic. This disease is closely associated with serotonin _1A (5-HT_1A) receptor and often treated by complex prescription containing Curcuma wenyujin Y. H. Chen et C. Ling. Therefore, we hypothesized that this herb contains bioactive compounds specially binding to the receptor. However, the rapid discovery of new ligands of 5-HT_1A receptor is still challenging due to the lack of efficient screening methods. To address this problem, we developed and characterized a novel approach for the rapid screening of ligands by using immobilized 5-HT_1A receptor as the chromatographic stationary phase. Briefly, haloalkane dehalogenase was fused at the C-terminal of 5-HT_1A receptor, and the modified 5-HT_1A receptor was immobilized on amino-microspheres by the reaction between haloalkane dehalogenase and 6-chlorohexanoic acid linker. Scanning electron microscope and X-ray photo-electron were used to characterize the morphology and element of the immobilized receptor. The binding of three specific ligands to 5-HT_1A receptor was investigated by two different methods. Moreover, we examined the feasibility of 5-HT_1A receptor colume in high throughput screening of new ligands from complex systems as exemplified by Curcuma wenyujin Y. H. Chen et C. Ling. Gweicurculactone, 2-hydroxy-1-(3,4-dihydroxybenzene)-7-(4′-hydroxybezene)-heptane and curcuminol F were identified as the ligands of 5-HT_1A receptor with the binding energies of −7.06 kcal/mol, −7.77 kcal/mol and −5.26 kcal/mol, respectively. Collectively, these results indicated that the immobilized 5-HT_1A receptor was capable of screening bioactive compound from complex system, providing an effective methodology for high throughput screening.

Association Between Sumatriptan Treatment During a Migraine Attack and Central 5-HT1B Receptor Binding

Importance

Triptans, the most efficient acute treatment for migraine attacks, are 5-HT1B/1D receptor agonists, but their precise mechanism of action is not completely understood. The extent to which triptans enter the central nervous system and bind to 5-HT1B receptors in the brain is unknown.

Objectives

To determine the occupancy of sumatriptan to central 5-HT1B receptors, and to investigate changes in brain serotonin levels during migraine attacks.

Design, Setting, and Participants

This study of 8 patients in Denmark used a within-participant design and was conducted from April 20, 2015, to December 5, 2016. Participants were otherwise healthy patients with untreated episodic migraine without aura, aged between 18 and 65 years, and recruited from the general community. Data analysis was performed from January 2017 to April 2018.

Interventions

All participants underwent positron emission tomographic scans after injection of [11C]AZ10419369, a specific 5-HT1B receptor radiotracer. All participants were scanned 3 times: (1) during an experimentally induced migraine attack, (2) after a subcutaneous injection of 6-mg subcutaneous sumatriptan, and (3) on a migraine attack-free day. Scans 1 and 2 were conducted on the same study day. Each scan lasted for 90 minutes.

Main Outcome and Measure

The primary outcome was the nondisplaceable binding potential of [11C]AZ10419369 across 7 brain regions involved in pain modulation. The binding potential reflects receptor density, and changes in binding potential reflects displacement of the radiotracer. The occupancy of sumatriptan was estimated from the 2 scans before and after sumatriptan administration.

Results

Eight patients with migraine were included in the study; of these participants, 7 (87%) were women. The mean (SD) age of participants on study day 1 was 29.5 (9.2) years and on study day 2 was 30.0 (8.9) years. Sumatriptan was associated with statistically significantly reduced 5-HT1B receptor binding across pain-modulating regions (mean [SD] binding potential, 1.20 [0.20] vs 1.02 [0.22]; P = .001), corresponding to a mean (SD) drug occupancy rate of 16.0% (5.3%). Furthermore, during migraine attacks, as compared with outside of attacks, 5-HT1B receptor binding was statistically significantly associated with reduced in pain-modulating regions (mean [SD] binding potential, 1.36 [0.22] vs 1.20 [0.20]; P = .02).

Conclusions and Relevance

Treatment with sumatriptan during migraine attacks appeared to be associated with a decrease in 5-HT1B receptor binding, a finding that is most likely associated with the binding of sumatriptan to central 5-HT1B receptors, but the contribution of ongoing cerebral serotonin release to the lower binding cannot be excluded; the migraine attack-associated decrease in binding could indicate that migraine attacks are associated with increases in endogenous serotonin.

5-HT1D receptors inhibit the monosynaptic stretch reflex by modulating C-fiber activity

The monosynaptic stretch reflex (MSR) plays an important role in feedback control of movement and posture but can also lead to unstable oscillations associated with tremor and clonus, especially when increased with spinal cord injury (SCI). To control the MSR and clonus after SCI, we examined how serotonin regulates the MSR in the sacrocaudal spinal cord of rats with and without a chronic spinal transection. In chronic spinal rats, numerous 5-HT receptor agonists, including zolmitriptan, methylergonovine, and 5-HT, inhibited the MSR with a potency highly correlated to their binding affinity to 5-HT_1D receptors and not other 5-HT receptors. Selective 5-HT_1D receptor antagonists blocked this agonist-induced inhibition, although antagonists alone had no action, indicating a lack of endogenous or constitutive receptor activity. In normal uninjured rats, the MSR was likewise inhibited by 5-HT, but at much higher doses, indicating a supersensitivity after SCI. This supersensitivity resulted from the loss of the serotonin transporter SERT with spinal transection, because normal and injured rats were equally sensitive to 5-HT after SERT was blocked or to agonists not transported by SERT (zolmitriptan). Immunolabeling revealed that the 5-HT_1D receptor was confined to superficial lamina of the dorsal horn, colocalized with CGRP-positive C-fibers, and eliminated by dorsal rhizotomy. 5-HT_1D receptor labeling was not found on large proprioceptive afferents or α-motoneurons of the MSR. Thus serotonergic inhibition of the MSR acts indirectly by modulating C-fiber activity, opening up new possibilities for modulating reflex function and clonus via pain-related pathways. NEW & NOTEWORTHY Brain stem-derived serotonin potently inhibits afferent transmission in the monosynaptic stretch reflex. We show that serotonin produces this inhibition exclusively via 5-HT_1D receptors, and yet these receptors are paradoxically mostly confined to C-fibers. This suggests that serotonin acts by gating of C-fiber activity, which in turn modulates afferent transmission to motoneurons. We also show that the classic supersensitivity to 5-HT after spinal cord injury results from a loss of SERT, and not 5-HT_1D receptor plasticity.

Effects of Chronic Sumatriptan and Zolmitriptan Treatment on 5-HT1 Receptor Expression and Function in Rats

Triptans are commonly used anti-migraine drugs and show agonist action mainly at serotonin 5-HT1B/1D/1F receptors. It is not known whether frequent or long-term treatment with these drugs would alter 5-HT receptor function. We investigated the effects of protracted (14-18 days) sumatriptan and zolmitriptan treatment in rats on 5-HT1 receptor mRNA expression and function in tissues related to migraine pathophysiology. RT-PCR analysis revealed that 5-HT1B/1D/1F receptor mRNA was reduced in the trigeminal ganglion after treatment with either triptan (reduction by: sumatriptan 39% and zolmitriptan 61% for 5-HT1B; 60% vs 41% for 5-HT1D; 32% vs 68% for 5-HT1F). Sumatriptan attenuated 5-HT1D receptor mRNA by 49% in the basilar artery, whereas zolmitriptan reduced 5-HT1B mRNA in this tissue by 70%. No change in 5-HT1 receptor mRNA expression was observed in coronary artery and dura mater. Chronic triptan treatment had no effect in two functional assays [sumatriptan mediated inhibition (50 mg/kg, i.p.) of electrically induced plasma protein extravasation in dura mater and 5-nonyloxytryptaminestimulated [35S]guanosine-5′-O-(3-thio)triphosphate binding in substantia nigra]. Furthermore, vasoconstriction to 5-HT in isolated basilar artery was not affected by chronic triptan treatment, while it was slightly reduced in coronary artery. We conclude that, although our treatment protocol altered mRNA receptor expression in several tissues relevant to migraine pathophysiology, it did not attenuate 5-HT1 receptor-dependent functions in rats.

Zolmitriptan Nasal Spray: A Review in Acute Migraine in Pediatric Patients 12 Years of Age or Older

The intranasal formulation of zolmitriptan, a selective serotonin 5-HT1B/1D agonist, was recently approved by the US Food and Drug Administration for the treatment of acute migraine in pediatric patients 12 years of age or older. This article summarizes the efficacy and tolerability of zolmitriptan (Zomig(®)) nasal spray (NS) in acute migraine in this patient group. Zolmitriptan NS 5 mg was more effective in relieving headache pain than placebo in two double-blind studies in pediatric patients 12-17 years of age with acute migraine. Furthermore, zolmitriptan NS 2.5 and 5 mg effectively relieved photophobia and phonophobia, and was associated with a faster return to normal daily activities than placebo. Zolmitriptan NS is rapidly absorbed from the nasal mucosa and is associated with a fast onset of action, with one study showing a significant difference versus placebo with regard to headache response 15 min after administration. In both trials, zolmitriptan NS was generally well tolerated, with no serious adverse events. In conclusion, zolmitriptan NS provides rapid, effective and generally well tolerated treatment of acute migraine in pediatric patients 12 years of age or older and may be of particular benefit for those with nausea or not easily able to swallow tablets.

Chemical mediators of migraine: preclinical and clinical observations

Migraine is a neurovascular disorder, and although the pathophysiology of migraine has not been fully delineated, much has been learned in the past 50 years. This knowledge has been accompanied by significant advancements in the way migraine is viewed as a disease process and in the development therapeutic options. In this review, we will focus on 4 mediators (nitric oxide, histamine, serotonin, and calcitonin gene-related peptide) which have significantly advanced our understanding of migraine as a disease entity. For each mediator we begin by reviewing the preclinical data linking it to migraine pathophysiology, first focusing on the vascular mechanisms, then the neuronal mechanisms. The preclinical data are then followed by a review of the clinical data which support each mediator's role in migraine and highlights the pharmacological agents which target these mediators for migraine therapy.

A PET study with [11C]AZ10419369 to determine brain 5-HT1B receptor occupancy of zolmitriptan in healthy male volunteers

Aim

To investigate the occupancy at brain 5-hydroxytryptamine (5-HT) 1B receptors in human subjects after administration of the antimigraine drug zolmitriptan.

Methods

Positron emission tomography (PET) studies were undertaken using the radioligand [11C]AZ10419369 in eight control subjects at baseline and after administration of zolmitriptan orodispersible tablets. The subjects were examined after two consecutive administrations of 10 mg zolmitriptan, approximately 1 week apart. Two of the subjects were subsequently examined after administration of 5 mg zolmitriptan. One week after the last administration of zolmitriptan five of the subjects underwent additional PET measurements without drug pretreatment.

Results

After administration of 10 mg zolmitriptan, mean receptor occupancy was 4–5%. No consistent changes in 5-HT1B receptor binding were observed for subjects who received 5 mg zolmitriptan. There was a statistically significant negative relationship between binding potential ( BPND) and plasma concentration of zolmitriptan and the active metabolite 183C91, respectively. All of the five subjects who were examined 1 week after dosing with zolmitriptan showed higher BPND post drug administration compared with baseline.

Conclusion

This is the first demonstration of CNS 5-HT1B receptor occupancy of a triptan. The findings are consistent with the low receptor occupancy previously reported in PET studies with agonists at other G protein coupled receptors.

Zolmitriptan: a novel portal hypotensive agent which synergizes with propranolol in lowering portal pressure

OBJECTIVE

Only a limited proportion of patients needing pharmacological control of portal hypertension are hemodynamic responders to propranolol. Here we analyzed the effects of zolmitriptan on portal pressure and its potential interaction with propranolol.

METHODS

ZOLMITRIPTAN, PROPRANOLOL OR BOTH WERE TESTED IN TWO RAT MODELS OF PORTAL HYPERTENSION: common bile duct ligation (CBDL) and CCl4-induced cirrhosis. In these animals we measured different hemodynamic parameters including portal venous pressure, arterial renal flow, portal blood flow and cardiac output. We also studied the changes in superior mesenteric artery perfusion pressure and in arterial wall cAMP levels induced by zolmitriptan, propranolol or both. Moreover, we determined the effect of splanchnic sympathectomy on the response of PVP to zolmitriptan.

RESULTS

In both models of portal hypertension zolmitriptan induced a dose-dependent transient descent of portal pressure accompanied by reduction of portal flow with only slight decrease in renal flow. In cirrhotic rats, splanchnic sympathectomy intensified and prolonged zolmitriptan-induced portal pressure descent. Also, propranolol caused more intense and durable portal pressure fall when combined with zolmitriptan. Mesenteric artery perfusion pressure peaked for about 1 min upon zolmitriptan administration but showed no change with propranolol. However propranolol enhanced and prolonged the elevation in mesenteric artery perfusion pressure induced by zolmitriptan. In vitro studies showed that propranolol prevented the inhibitory effects of β2-agonists on zolmitriptan-induced vasoconstriction and the combination of propranolol and zolmitriptan significantly reduced the elevation of cAMP caused by β2-agonists.

CONCLUSION

Zolmitriptan reduces portal hypertension and non-selective beta-blockers can improve this effect. Combination therapy deserves consideration for patients with portal hypertension failing to respond to non-selective beta-blockers.

Reduction of spinal sensory transmission by facilitation of 5-HT1B/D receptors in noninjured and spinal cord-injured humans

Activation of receptors by serotonin (5-HT1) and norepinephrine (α2) on primary afferent terminals and excitatory interneurons reduces transmission in spinal sensory pathways. Loss or reduction of descending sources of serotonin and norepinephrine after spinal cord injury (SCI) and the subsequent reduction of 5-HT1/α2 receptor activity contributes, in part, to the emergence of excessive motoneuron activation from sensory afferent pathways and the uncontrolled triggering of persistent inward currents that depolarize motoneurons during muscle spasms. We tested in a double-blind, placebo-controlled study whether facilitating 5-HT1B/D receptors with the agonist zolmitriptan reduces the sensory activation of motoneurons during an H-reflex in both noninjured control and spinal cord-injured participants. In both groups zolmitriptan, but not placebo, reduced the size of the maximum soleus H-reflex with a peak decrease to 59% (noninjured) and 62% (SCI) of predrug values. In SCI participants we also examined the effects of zolmitriptan on the cutaneomuscular reflex evoked in tibialis anterior from stimulation to the medial arch of the foot. Zolmitriptan, but not placebo, reduced the long-latency, polysynaptic component of the cutaneomuscular reflex (first 200 ms of reflex) by ∼50%. This ultimately reduced the triggering of the long-lasting component of the reflex (500 ms poststimulation to end of reflex) known to be mediated by persistent inward currents in the motoneuron. These results demonstrate that facilitation of 5-HT1B/D receptors reduces sensory transmission in both monosynaptic and polysynaptic reflex pathways to ultimately reduce long-lasting reflexes (spasms) after SCI.

Pharmacokinetic evaluation of zolmitriptan for the treatment of migraines

INTRODUCTION

Migraine is a multifactorial neurovascular disorder characterized by recurrent episodes of disabling pain attacks, accompanied with gastrointestinal, neurological systems dysfunction. The pharmacologic treatment of migraine is classically divided in the management of the acute attack and preventive strategies. Acute treatments consist of triptan, ergot, opioid, antiemetic and NSAIDs.

AREAS COVERED

This article discusses pharmacodynamics and pharmacokinetics of zolmitriptan . The data were obtained by searching the following keywords in MEDLINE: zolmitriptan, pharmacokinetics, pharmacodynamics, triptans, migraine, menstrual-related migraine, cluster headache, relatively to the period 1989 - 2012.

EXPERT OPINION

Zolmitriptan has been considered effective treatment in the acute phase of migraine, menstrual-related migraine and cluster headache attacks. Pharmacokinetic parameters may vary as a consequence of gender differences, inter- and intra-subjects variability and delivery system. Zolmitriptan was developed with the aim of obtaining a lipophilic compound in order to be more rapidly absorbed and centrally active. Pharmacologically, pharmacokinetic parameters are responsible for its wide efficacy and the limited adverse effect profile.

Autoradiographic Mapping of 5-HT(1B/1D) Binding Sites in the Rhesus Monkey Brain Using [carbonyl-C]zolmitriptan

Zolmitriptan is a serotonin 5-HT(1B/1D) receptor agonist that is an effective and well-tolerated drug for migraine treatment. In a human positron emission tomography study, [(11)C]zolmitriptan crossed the blood-brain barrier but no clear pattern of regional uptake was discernable. The objective of this study was to map the binding of [(11)C]zolmitriptan in Rhesus monkey brain using whole hemisphere in vitro autoradiography with [(11)C]zolmitriptan as a radioligand. In saturation studies, [(11)C]zolmitriptan showed specific (90%) binding to a population of high-affinity binding sites (Kd 0.95-5.06 nM). There was regional distribution of binding sites with the highest density in the ventral pallidum, followed by the external globus pallidus, substantia nigra, visual cortex, and nucleus accumbens. In competitive binding studies with 5-HT(1) receptor antagonists, [(11)C]zolmitriptan binding was blocked by selective 5-HT(1B) and 5-HT(1D) ligands in all target areas. There was no appreciable change in binding with the addition of a 5-HT(1A) receptor antagonist.

Polysynaptic excitatory postsynaptic potentials that trigger spasms after spinal cord injury in rats are inhibited by 5-HT1B and 5-HT1F receptors

Sensory afferent transmission and associated spinal reflexes are normally inhibited by serotonin (5-HT) derived from the brain stem. Spinal cord injury (SCI) that eliminates this 5-HT innervation leads to a disinhibition of sensory transmission and a consequent emergence of unusually long polysynaptic excitatory postsynaptic potentials (EPSPs) in motoneurons. These EPSPs play a critical role in triggering long polysynaptic reflexes (LPRs) that initiate muscles spasms. In the present study we examined which 5-HT receptors modulate the EPSPs and whether these receptors adapt to a loss of 5-HT after chronic spinal transection in rats. The EPSPs and associated LPRs recorded in vitro in spinal cords from chronic spinal rats were consistently inhibited by 5-HT(1B) or 5-HT(1F) receptor agonists, including zolmitriptan (5-HT(1B/1D/1F)) and LY344864 (5-HT(1F)), with a sigmoidal dose-response relation, from which we computed the 50% inhibition (EC(50)) and potency (-log EC(50)). The potencies of 5-HT receptor agonists were highly correlated with their binding affinity to 5-HT(1B) and 5-HT(1F) receptors, and not to other 5-HT receptors. Zolmitriptan also inhibited the LPRs and general muscle spasms recorded in vivo in the awake chronic spinal rat. The 5-HT(1B) receptor antagonists SB216641 and GR127935 and the inverse agonist SB224289 reduced the inhibition of LPRs by 5-HT(1B) agonists (zolmitriptan). However, when applied alone, SB224289, SB216641, and GR127935 had no effect on the LPRs, indicating that 5-HT(1B) receptors do not adapt to chronic injury, remaining silent, without constitutive activity. The reduction in EPSPs with zolmitriptan unmasked a large glycine-mediated inhibitory postsynaptic current (IPSC) after SCI. This IPSC and associated chloride current reversed at -73 mV, slightly below the resting membrane potential. Zolmitriptan did not change motoneuron properties. Our results demonstrate that 5-HT(1B/1F) agonists, such as zolmitriptan, can restore inhibition of sensory transmission after SCI without affecting general motoneuron function and thus may serve as a novel class of antispastic drugs.

Motoneuron excitability and muscle spasms are regulated by 5-HT2B and 5-HT2C receptor activity

Immediately after spinal cord injury (SCI), a devastating paralysis results from the loss of brain stem and cortical innervation of spinal neurons that control movement, including a loss of serotonergic (5-HT) innervation of motoneurons. Over time, motoneurons recover from denervation and function autonomously, exhibiting large persistent calcium currents (Ca PICs) that both help with functional recovery and contribute to uncontrolled muscle spasms. Here we systematically evaluated which 5-HT receptor subtypes influence PICs and spasms after injury. Spasms were quantified by recording the long-lasting reflexes (LLRs) on ventral roots in response to dorsal root stimulation, in the chronic spinal rat, in vitro. Ca PICs were quantified by intracellular recording in synaptically isolated motoneurons. Application of agonists selective to 5-HT(2B) and 5-HT(2C) receptors (including BW723C86) significantly increased the LLRs and associated Ca PICs, whereas application of agonists to 5-HT(1), 5-HT(2A), 5-HT(3), or 5-HT(4/5/6/7) receptors (e.g., 8-OH-DPAT) did not. The 5-HT(2) receptor agonist-induced increases in LLRs were dose dependent, with doses for 50% effects (EC(50)) highly correlated with published doses for agonist receptor binding (K(i)) at 5-HT(2B) and 5-HT(2C) receptors. Application of selective antagonists to 5-HT(2B) (e.g., RS127445) and 5-HT(2C) (SB242084) receptors inhibited the agonist-induced increase in LLR. However, antagonists that are known to specifically be neutral antagonists at 5-HT(2B/C) receptors (e.g., RS127445) had no effect when given by themselves, indicating that these receptors were not activated by residual 5-HT in the spinal cord. In contrast, inverse agonists (such as SB206553) that block constitutive activity at 5-HT(2B) or 5-HT(2C) receptors markedly reduced the LLRs, indicating the presence of constitutive activity in these receptors. 5-HT(2B) or 5-HT(2C) receptors were confirmed to be on motoneurons by immunolabeling. In summary, 5-HT(2B) and 5-HT(2C) receptors on motoneurons become constitutively active after injury and ultimately contribute to recovery of motoneuron function and emergence of spasms.

Comparison of the vasoconstrictor effects of the calcitonin gene-related peptide receptor antagonist telcagepant (MK-0974) and zolmitriptan in human isolated coronary arteries

Studies were conducted in human isolated coronary arteries to explore the vascular effects of the calcitonin gene-related peptide (CGRP) receptor antagonist telcagepant and to compare its coronary vasoconstrictive potential to that of zolmitriptan. KCl precontracted coronary vessels were shown to relax to human alphaCGRP, with the CGRP-mediated vasorelaxation completely blocked with 30 microM telcagepant. In coronary vessels at basal tone, zolmitriptan caused a concentration-dependent contraction (pEC50 = 6.9 +/- 0.1; slope 0.94), with the greatest contraction obtained between 1 and 10 microM in most tissues. In contrast, telcagepant at concentrations up to 30 microM evoked no change in contractile tone. These findings suggest the potential for CGRP receptor antagonists to exert antimigraine efficacy in the absence of adverse effects on coronary tone.

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.

Designing selective, high affinity ligands of 5-HT1D receptor by covalent dimerization of 5-HT1F ligands derived from 4-fluoro-N-[3-(1-methyl-4-piperidinyl)-1H-indol-5-yl]benzamide

We demonstrate here that covalent dimerization of 5-HT 1 ligands is an effective design strategy to modulate affinity and selectivity of 5-HT 1 ligands. This approach was applied to LY-334370, a selective agonist of 5-HT 1F receptor, to generate structurally well-defined divalent molecules. Radioligand binding assays to three cloned 5-HT 1 receptor subtypes (5-HT 1B, 5-HT 1D, 5-HT 1F) demonstrated that the affinity of a series of homologous dimers varied significantly upon exploration of three structural variables (linker length, attachment position, functionality). In particular, the series of C 3-to-C 3 linked dimers derived from a monomer ( 3) showed high binding affinity to 5-HT 1D (for example, K i approximately 0.3 nM for dimer 8) but did not bind to 5-HT 1F ( K i > 0.01 mM), providing >10000-fold subtype selectivity. Results from a functional assay (rabbit saphenous vein contraction) demonstrate that certain dimers are 5-HT 1 receptor agonists.

Determination of zolmitriptan enantiomers in rat liver microsomes by chiral high performance liquid chromatography with ?uorescence detection

A selective chiral high performance liquid chromatographic method was developed and validated to separate and quantify the enantiomers of a new potent selective 5-HT(1B/1D) receptor partial agonist, S-zolmitriptan, and its antipode in rat liver microsomes induced with beta-naphtho flavone. S- and R-zolmitriptan were extracted from rat hepatic microsomal incubates with chloroform/isopropanol (75:25, v/v), and were separated on a narrow-bore enantioselective normal phase Chiralpak AD-H column (250 x 0.46 mm) with hexane-isopropanol-triethylamine (72/28/0.25, v/v/v) as mobile phase and fluorescence detection with emission at 350 nm and excitation at 291 nm. The calibration curves were linear for R- and S-zolmitriptan concentration over the range 0.1-5.0 microg/mL (r = 0.9996 and 0.9999), and the limits of quantitation were 0.1 microg/mL. The metabolism and interaction of the enantiomers of zolmitriptan in treated hepatic microsomes were investigated using chiral HPLC. There was significant difference between the disposition of the S- and R-zolmitriptan when racemic zolmitriptan or single enantiomers of zolmitriptan were incubated for 5, 10 and 20 min, suggesting that the metabolism of zolmitriptan in rat liver microsomes is enantioselective. In addition, there was also a significant difference between the IC(50) of R- to S-zolmitriptan and S- to R-zolmitriptan (IC(50S/R)/IC(50R/S) = 45.2). This indicated that the disposition process favored the S-form of zolmitriptan.

Zolmitriptan Nasal Spray Exhibits Good Long-Term Safety and Tolerability in Migraine: Results of the INDEX Trial

BACKGROUND

Previous studies have shown that zolmitriptan 5 mg nasal spray has a fast onset of action, high efficacy, and good tolerability in the acute treatment of migraine. Objective.-This open-label, noncomparative, multicenter, multinational phase III study was designed to further evaluate the long-term safety and tolerability of zolmitriptan 5 mg nasal spray in a population of migraineurs largely naive to triptan nasal sprays who treated multiple migraine attacks over a 1-year period.

METHODS

Patients were required to have an established diagnosis of migraine with or without aura (based on International Headache Society criteria), a high frequency of migraine attacks, and were allowed to treat migraine with any baseline headache intensity. A secondary objective of the study was to assess the long-term efficacy of zolmitriptan nasal spray. A subgroup analysis aimed to determine whether rhinitis had any influence on outcomes of treatment.

RESULTS

The safety population consisted of 538 patients who treated 20,717 migraine attacks with zolmitriptan 5 mg nasal spray. Overall, adverse events occurred in 32.8% of attacks, and led to treatment withdrawal in 4.5% of patients. The most common adverse events were unusual taste (19.0%) and paresthesia (6.8%). Adverse events were generally of mild intensity, transient, and well tolerated, showing a decline in incidence over time. Serious adverse events were rare. The presence of rhinitis and use of a second dose of trial medication had no effect on the incidence of adverse events. At 2 hours, 53.8% of attacks treated with zolmitriptan nasal spray 5 mg were rendered pain free. The highest 2-hour pain free rates were seen for headaches of mild baseline intensity (83.3%), followed by headaches of moderate (56.5%), and severe (32.2%) baseline intensity. The 2-hour pain-free rate remained consistent throughout the study period. The presence of rhinitis had no effect on efficacy.

CONCLUSIONS

Zolmitriptan 5 mg nasal spray demonstrated a well-tolerated and efficacious profile in the acute treatment of multiple migraine attacks over a 1-year period.

Part II: clinical efficacy and tolerability of zolmitriptan orally disintegrating tablet in the acute treatment of migraine

Controlled clinical trials and extensive clinical use of conventional oral tablets of zolmitriptan, a selective agonist of serotonin1B/1D receptors, have proven the compound to be fast-acting, highly effective, and well-tolerated in the acute treatment of migraine. An orally disintegrating tablet (ODT) of zolmitriptan that dissolves on the tongue without the need for fluid intake has been developed in order to provide an acceptable, convenient alternative for patients who prefer not to, or cannot, take conventional tablets. A fast onset of effective, sustained pain relief was predicted for zolmitriptan ODT on the basis of its bioequivalence with the conventional tablet, which has been confirmed in three randomised, double-blind, placebo-controlled trials of zolmitriptan ODT in the acute treatment of migraine. Compared with placebo, significantly higher proportions of patients treated with zolmitriptan ODT responded to treatment (reduction of moderate or severe headache to mild or no pain) as early as 30 minutes after dosing. Headache response was maintained at 24 hours in significantly higher proportions of patients receiving zolmitriptan ODT compared with placebo. Zolmitriptan ODT also resulted in significantly greater pain-free rates than placebo as early as 1 hour after dosing. Zolmitriptan ODT relieved patients of other migraine-associated symptoms, including nausea, photophobia and phonophobia, and enabled >50% of patients to resume normal daily activities 2 hours after dosing. Adverse events observed with zolmitriptan ODT were similar to those associated with the serotonin1B/1D agonists as a class, and were generally transient and of mild or moderate intensity.

Preclinical neuropharmacology of naratriptan

The basic CNS neuropharmacology of naratriptan is reviewed here. Naratriptan is a second-generation triptan antimigraine drug, developed at a time when CNS activity was thought not to be relevant to its therapeutic effect in migraine. It was, however, developed to be a more lipid-soluble, more readily absorbed and less readily metabolized variant on preexisting triptans and these variations conferred on it a higher CNS profile. Naratriptan is a 5-HT(1B/1D) receptor agonist with a highly selective action on migraine pain and nausea, without significant effect on other pain or even other trigeminal pain. Probable sites of therapeutic action of naratriptan include any or all of: the cranial vasculature; the peripheral terminations of trigeminovascular sensory nerves; the first-order synapses of the trigeminovascular sensory system; the descending pain control system; and the nuclei of the thalamus. Naratriptan may prevent painful dilatation of intracranial vessels or reverse such painful dilatation. Naratriptan can prevent the release of sensory peptides and inhibit painful neurogenic vasodilatation of intracranial blood vessels. At the first order synapse of the trigeminal sensory system, naratriptan can selectively suppress neurotransmission from sensory fibers from dural and vascular tissue, while sparing transmission from other trigeminal fibers, probably through inhibition of neuropeptide transmitter release. In the periaqueductal gray matter and in the nucleus raphe magnus, naratriptan selectively activates inhibitory neurons which project to the trigeminal nucleus and spinal cord and which exert inhibitory influences on trigeminovascular sensory input. Naratriptan has also a therapeutic effect on the nausea of migraine, possibly exerting its action at the level of the nucleus tractus solitarius via the same mechanisms by which it inhibits trigeminovascular nociceptive input. The incidence of naratriptan-induced adverse effects in the CNS is low and it is not an analgesic for pain other than that of vascular headache. In patients receiving selective serotonin uptake inhibitors (SSRIs) naratriptan may cause serotonin syndrome-like behavioral side effects. The mechanism of action involved in the production of behavioral and other CNS side effects of naratriptan is unknown.

Nitrergic and glutamatergic neuronal mechanisms at the trigeminovascular first-order synapse

Nitric oxide (NO) donors such as glyceryl trinitrate cause headache, which suggests involvement of NO in trigeminovascular sensory processing. Sensory transmission at first-order synapses is believed to involve glutamate and the question arises as to whether it is also involved in trigeminovascular sensation and whether it might interact with nitrergic mechanisms. We investigated these questions at the first central synapse in the trigeminovascular sensory system of the cat. Neuronal action potentials in the trigeminal nucleus were recorded while the superior sagittal sinus (SSS) or facial receptive field (RF) were stimulated electrically. Drugs, including the neuronal excitant glutamate, were applied to neurons via microiontophoresis. Results were obtained from 152 neurons activated with A-delta latencies by SSS stimulation and by glutamate. The NO donor S-nitrosoglutathione (SNOG, 50 nA) was applied iontophoretically to 41 neurons during SSS stimulation and 13 neurons during pulsatile glutamate ejection. Responses to both modes of stimulation were enhanced by SNOG; the proportion of neurons enhanced was 56% to SSS stimulation and 59% to glutamate. The inhibitor of nitric oxide synthase (NOS), N(omega)-propyl-L-arginine (p-ARG, 50 nA) was applied iontophoretically to 17 neurons during stimulation of SSS and to 10 neurons during pulsatile glutamate ejection. Responses to both stimuli were suppressed by p-ARG: The proportion of neurons suppressed were: to SSS stimulation 59% and to glutamate 80%. Microiontophoretic ejection of eletriptan (50 nA) reversibly suppressed responses of neurons to SSS stimulation, to RF electrical stimulation and to pulsatile iontophoretic application of glutamate. This suppression of responses was antagonised by the concurrent local iontophoretic application of the 5-HT1B/1D receptor antagonist GR127935 or by concurrent iontophoretic application of the selective 5-HT1D receptor antagonist BRL155732. These results suggest that glutamatergic mechanisms are important in sensory transmission in the trigeminovascular system and that they can be modulated by nitrergic and serotonergic mechanisms.

Speed of onset and efficacy of zolmitriptan nasal spray in the acute treatment of migraine: a randomised, double-blind, placebo-controlled, dose-ranging study versus zolmitriptan tablet

OBJECTIVE

Zolmitriptan oral tablet is highly effective and well tolerated in the acute treatment of migraine with and without aura in adults. A nasal spray formulation has now been developed. The objective of this study was to compare the efficacy and tolerability of fixed doses of zolmitriptan administered via a nasal spray with placebo and zolmitriptan oral tablet in the acute treatment of migraine.

PATIENTS AND STUDY DESIGN

This was a randomised, double-blind, double-dummy, placebo-controlled, parallel-group, multicentre, dose-ranging study. 1547 patients aged 18-65 years with an established diagnosis of migraine with or without aura (as defined by International Headache Society criteria) who had at least a 1-year history of migraine and an age of onset <50 years were included. Patients were able to distinguish typical migraine from nonmigraine headaches and had experienced an average of one to six migraine headaches per month during the 2 months preceding the study. Patients were randomised to zolmitriptan (Zomig) The use of tradenames is for product identification purposes only and does not imply endorsement.) nasal spray (5.0, 2.5, 1.0 or 0.5 mg), zolmitriptan oral tablet (2.5mg) or placebo for the treatment of three moderate or severe migraine attacks. The primary outcome measure was headache response at 2 hours following treatment, defined as reduced intensity of migraine pain (using a scale of none, mild, moderate or severe) from severe or moderate at baseline to mild or no pain at 2 hours after treatment. Secondary outcome measures included early headache response at 15, 30 and 45 minutes and headache response at 1 and 4 hours postdose, as well as pain-free rates at 15, 30 and 45 minutes and 1, 2 and 4 hours postdose. Laboratory assessments, vital signs, 12-lead ECGs and nose and throat examinations were performed at screening and follow-up visits. Adverse events were recorded throughout the study using Coding Symbols for Thesaurus of Adverse Reaction Terms (COSTART) terminology.

RESULTS

Each dose of zolmitriptan nasal spray produced a greater 2-hour headache response rate than placebo (70.3%, 58.6%, 54.8% and 41.5% for zolmitriptan nasal spray 5.0, 2.5, 1.0 and 0.5mg, compared with 30.6% for placebo [all p < 0.001 vs placebo]). The 2-hour headache response rate for zolmitriptan nasal spray 5.0mg was significantly higher than that of the zolmitriptan 2.5mg oral tablet (61.3%; p < 0.05), while comparisons of nasal spray 0.5, 1.0 and 2.5mg with zolmitriptan 2.5mg oral tablet were not statistically significant. The nasal spray 5.0 and 2.5mg showed a rapid onset of action, with a significant difference in headache response compared with placebo from 15 minutes through 4 hours after administration and a significant difference between the nasal spray 5.0mg and 2.5mg oral tablet from 15 minutes through to 2 hours (the other nasal spray doses were not statistically significant compared with 2.5mg oral tablet). Zolmitriptan nasal spray resulted in pain-free rates that were dose dependent. While all doses from 1.0 mg upwards produced significant pain-free outcomes from 30 minutes versus placebo, only the 5.0mg dose produced pain-free rates significantly superior to both placebo and the 2.5mg oral tablet. Zolmitriptan nasal spray was well tolerated, with the most common adverse events being unusual taste and paresthesia. The majority of adverse events were of short duration and mild or moderate intensity. Only ten patients were withdrawn from the trial because of adverse events. Serious adverse events were reported by nine patients after taking study medication, but none was considered to be causally related to study medication. Zolmitriptan was not associated with any clinically significant changes in laboratory test values or vital signs.

CONCLUSION

All doses of zolmitriptan nasal spray produced significant 2-hour headache response rates compared with placebo. The 5.0 and 2.5mg doses were also significantly more effective than placebo for the majority of secondary efficacy measures. Zolmitriptan nasal spray 5.0mg provided a headache response statistically superior to both placebo and the 2.5mg tablet as early as 15 minutes after administration, while demonstrating pain-free outcomes significantly superior to placebo and the 2.5mg tablet as early as 30 minutes after administration. All doses of zolmitriptan nasal spray were well tolerated, resulting in an optimal therapeutic index and clinical recommendation for the 5.0mg dose.

In vitro expression and pharmacology of the 5-HT7-like receptor present in the mosquito Aedes aegypti tracheolar cells and hindgut-associated nerves

We have previously reported the cloning of a 5-hydroxytryptamine receptor (Aedes 5-HT7-like receptor) from adult Aedes aegypti. For functional expression of the Aedes 5-HT7-like receptor, CHO-K1 cells were stably transfected with a receptor expression construct, pC5-HT7. The Aedes 5-HT7-like receptor positively coupled to Gs protein, increasing intracellular cAMP in response to 5-HT; adenylyl cyclase activity was induced in a concentration-dependent, saturable manner. Only 5-HT, and not octopamine, dopamine or tyramine, caused the induction of cAMP. At 10 nM 5-HT a weak synergism was observed between octopamine and 5-HT. Other known agonists of the mammalian 5-HT7 receptor were tested. Their order of potency was: 5-HT >> 5-CT = 8-OH-DPAT >> pimozide. This is the first report on the functional expression of a mosquito neurohormone receptor.

Tolerability and consistency of effect of zolmitriptan nasal spray in a long-term migraine treatment trial

OBJECTIVES

To primarily assess the tolerability of zolmitriptan (Zomig) nasal spray 5mg in the long-term treatment of migraine, as well as determine efficacy and consistency of effect over time (up to 1 year).

METHODS

This randomised, double-blind-to-dose, parallel-group, multicentre study was designed as a two-phase, crossover trial with a total duration of 1 year. In the pre-crossover phase, 1,093 patients aged 18-65 years with an established diagnosis of migraine with or without aura received intranasal zolmitriptan 5, 2.5, 1 or 0.5mg for the treatment of mild, moderate or severe migraine attacks. When a headache persisted or recurred, a second dose of zolmitriptan nasal spray (or other approved escape medication) was permitted 2 hours post-administration but no later than 24 hours after the first dose. In the post-crossover phase, once a placebo-controlled, dose-finding study had established 5mg as the dose with the optimal clinical utility, all patients were crossed over under blinded conditions to receive this dose. As this was primarily a safety study, the primary endpoints for the study were the incidence and nature of all serious adverse events (at any time before or after administration) and nonserious adverse events (within 24 hours of administration), as well as the incidence of clinically significant abnormalities in either ECG or haematology and clinical chemistry parameters. Nose and throat examinations were performed before and after the study at 30 predetermined trial centres. Other endpoint measures included headache response rate, pain-free assessments, reduction in headache intensity, time to resumption of normal activities and consistency of headache response. Efficacy rates were measured in 90-day intervals up to a period of 360 days.

RESULTS

Zolmitriptan nasal spray 5mg was well tolerated, with only 1.9% of patients withdrawing from the 12-month long-term trial because of adverse events. Adverse events occurred in 22.1% of attacks treated with zolmitriptan nasal spray 5mg, and the majority were of short duration and mild or moderate intensity. Serious adverse events occurred in 0.2% of attacks treated with zolmitriptan nasal spray 5mg. There was no evidence of increased incidence of adverse events with increasing duration of treatment. Nasopharyngeal adverse events were reported in 5.5% of attacks treated with zolmitriptan nasal spray 5mg. Again, events were generally transient and of mild intensity. For the 1,093 patients who treated 13,806 attacks during the pre-crossover phase, headache response rates at 2 hours over all attacks were 73.2%, 70.5%, 49.9% and 41.5% for zolmitriptan nasal spray 5, 2.5, 1 and 0.5mg, respectively. Pain-free rates at 2 hours over all attacks were 51.5%, 48.1%, 24.7% and 21.8%, respectively. For the 783 patients receiving the 5mg dose in either the pre- or post-crossover phases, the 2-hour headache response rates were 72.9%, 74.4%, 74.6% and 74.1% for the four 90-day periods between day 0 and day 360. Normal activities were resumed within 2 hours in 60.4% of attacks. Long-term usage of zolmitriptan nasal spray 5mg was also associated with a consistently effective response, with 57.8% of patients experiencing a 2-hour headache response in over 75% of attacks. The majority of patients (70.3%) rated their overall satisfaction with zolmitriptan nasal spray 5mg as good or excellent.

CONCLUSION

Zolmitriptan nasal spray 5mg provides good tolerability and efficacy in long-term use in a clinical setting, with consistently high 2-hour headache and pain-free rates. This combination of benefits translates to high patient satisfaction with this formulation of zolmitriptan.

5-HT1F receptor agonists in acute migraine treatment: a hypothesis

Serotonin-1F receptor (5-HT1F) agonists may relieve acute migraine without vasoconstriction. We conducted a review of preclinical and clinical data that assessed the potential link between migraine and 5-HT1F activation. (i) A high correlation exists between the potency of various 5-HT1 receptor agonists in the guinea pig dural plasma protein extravasation assay and their 5-HT1F receptor binding affinity. (ii) 5-HT1F receptors are on the trigeminal system, and may participate in blocking migraine pain transmission through the trigeminal ganglion and nucleus caudalis. (iii) 5-HT1F receptors are located on glutamate-containing neurones and their activation might inhibit glutamate release; glutamate excess may play a role in migraine. (iv) Selective 5-HT1F receptor agonists (LY334370; LY344864) are effective in preclinical migraine models and are non-vasoconstrictive. (v) LY334370 is effective in acute migraine, and does not cause any symptoms/signs of coronary vasoconstriction. Preclinical experiments and clinical observations argue for a role of selective 5-HT1F agonists in migraine.

Molecular Mechanisms of Migraine

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

Triptans reduce the inflammatory response in bacterial meningitis

Severe headache and meningism provide clear evidence for the activation of trigeminal neurotransmission in meningitis. The authors assessed the antiinflammatory potential of 5HT1B/D/F receptor agonists (triptans), which inhibit the release of proinflammatory neuropeptides from perivascular nerve fibers. In a 6-hour rat model of pneumococcal meningitis, zolmitriptan and naratriptan reduced the influx of leukocytes into the cerebrospinal fluid, and attenuated the increase of regional cerebral blood flow. Elevated intracranial pressure as well as the brain water content at 6 hours was reduced by triptans. These effects were partially reversed by a specific 5HT1D as well as by a specific 5HT1B receptor antagonist. Meningitis caused a depletion of calcitonin gene-related peptide (CGRP) and substance P from meningeal nerve fibers, which was prevented by zolmitriptan and naratriptan. In line with these findings, patients with bacterial meningitis had significantly elevated CGRP levels in the cerebrospinal fluid. In a mouse model of pneumococcal meningitis, survival and clinical score at 24 hours were significantly improved by triptan treatment. The findings suggest that, besides mediating meningeal nociception, meningeal nerve fibers contribute to the inflammatory cascade in the early phase of bacterial meningitis. Adjunctive treatment with triptans may open a new therapeutic approach in the acute phase of bacterial meningitis.

Review of zolmitriptan and its clinical applications in migraine

Preclinical studies have shown that zolmitriptan is a selective serotonin 5-HT(1B/1D) receptor agonist (triptan). Randomised, placebo-controlled, double-blind trials in patients with migraine have shown that zolmitriptan has good efficacy measured using 2 h response and pain-free rates. Migraine-associated symptoms, including nausea, photophobia and phonophobia, are also improved with zolmitriptan. Oral zolmitriptan (2.5 and 5 mg) has an onset of action within 45 min and efficacy is sustained in most patients who respond at 2 h. The orally-disintegrating zolmitriptan tablet has the advantage that it may be taken immediately, without the need for additional fluids, any time a migraine headache occurs. Patients may benefit in terms of improved efficacy from the convenience of the disintegrating tablet, since there is evidence that taking triptan therapy as early as possible in an attack is advantageous. For similar reasons, as well as improved efficacy, a nasal spray formulation is in development. Zolmitriptan is effective in the treatment of migraine associated with menses and migraine with aura. There is no tachyphylaxis following repeated doses for multiple attacks of migraine over a prolonged period of time. Compared to placebo, the incidence of persistent migraine headache is reduced by zolmitriptan and recurrent migraine headache occurs less frequently. Zolmitriptan has also shown efficacy in the treatment of persistent and/or recurrent migraine headache. Comparative clinical studies have shown overall that zolmitriptan has similar or superior efficacy to sumatriptan in the treatment of migraine. Specifically, zolmitriptan 2.5 mg was significantly more effective than sumatriptan 25 or 50 mg according to a number of end points, including headache response at 2 h. Oral zolmitriptan is also effective in the acute treatment of cluster headache. Zolmitriptan is generally well tolerated, with most adverse events being mild-to-moderate, transient and resolving without intervention or the need for treatment withdrawal. The consistent efficacy in treating all types of migraine and the choice of available formulations make zolmitriptan acceptable to patients and a suitable first-line therapy for the treatment of migraine.

The role of 5-HT1B and 5-HT1D receptors in the selective inhibitory effect of naratriptan on trigeminovascular neurons

The importance of 5-HT(1B) and 5-HT(1D) receptors in the actions of the anti-migraine drug naratriptan was investigated using the relatively selective 5-HT(1) receptor ligands SB224289 and BRL15572. Electrical stimulation of the superior sagittal sinus (SSS) in cats activated neurones in the trigeminal nucleus caudalis. Facial receptive fields (RF) were also electrically stimulated to activate the same neurones. Responses of these neurones to SSS stimulation were suppressed by iontophoretic application of naratriptan (5-50 nA). There were two distinct populations of neurones in the nucleus--those in deeper laminae in which the responses to SSS and RF stimulation were equally suppressed by naratriptan ('non-selective') and more superficial neurones in which only the SSS responses were suppressed by naratriptan ('selective'). Concurrent micro-iontophoretic application (50 nA) of the 5-HT(1D) antagonist BRL15572 antagonised the suppression by naratriptan of the response of 'selective' cells to SSS stimulation. Iontophoretic application of SB224289 (50 nA), a 5-HT(1B) antagonist, antagonised the suppression by naratriptan of responses of 'non-selective' cells to RF stimulation and, to a lesser extent, also antagonised the suppression of responses to SSS stimulation. Intravenous administration of SB224289 antagonised the suppression only of RF responses of "non-selective" neurons by naratriptan and intravenous administration of BRL15572 antagonised the suppression only of SSS responses of "selective" neurons by naratriptan. These results suggest that the response of nucleus caudalis neurons to stimulation of the sagittal sinus can be modulated by both 5-HT(1B) and 5-HT(1D) receptor activation, with the 5-HT(1D) receptors perhaps playing a greater role. The response to RF stimulation is more influenced by 5-HT(1B) receptor modulation with 5-HT(1D) receptors being less important. Therefore, this suggests that selective 5-HT(1D) agonists may be able to target the neuronal population, which is selectively involved in the transmission of dural inputs. We conclude that the central terminals of trigeminal primary afferent fibres contain 5-HT(1B) and 5-HT(1D) receptors. Primary afferents from the dura mater may predominantly express 5-HT(1D) receptors, while facial afferents may predominantly express 5-HT(1B) receptors. Activation of 5-HT(1D) receptors in particular may be important in the anti-migraine effect of naratriptan.

Zolmitriptan orally disintegrating tablet is effective in the acute treatment of migraine

A new formulation of zolmitriptan has been developed that dissolves on the tongue without the need for additional fluid intake. In this double-blind, parallel study, 471 patients were randomized to receive the zolmitriptan orally disintegrating tablet 2.5 mg (n=231) or matching placebo (n=240) to treat a single moderate or severe migraine. Headache relief following zolmitriptan 2.5 mg (63%) was significantly greater than with placebo (22%) at 2 h post-dose (primary endpoint; P < 0.0001). The zolmitriptan orally disintegrating tablet was also significantly more effective than placebo for 1-, 2- and 4-h pain-free response (8% vs. 3%, P=0.0207, 27% vs. 7%, P < 0.0001, and 37% vs. 11%, P < 0.0001, respectively). Of those patients stating a preference, 70% of patients preferred the orally disintegrating tablet to a conventional tablet. Zolmitriptan orally disintegrating tablets are an effective and convenient alternative to a conventional tablet, allowing migraine attacks to be treated anytime a migraine strikes, which can facilitate earlier treatment.

4991W93, a potent blocker of neurogenic plasma protein extravasation, inhibits trigeminal neurons at 5-hydroxytryptamine (5-HT1B/1D) agonist doses

Triptans share the pharmacological profile of being 5-hydroxytryptamine (5-HT1B/1D) agonists and having potent anti-migraine activity. The conformationally restricted zolmitriptan analogue 4991W93 was developed as a potent, and at low doses, specific, non-vasconstrictor inhibitor of neurogenic dural plasma protein extravasation. Here, we sought to study the effect of 4991W93 at plasma protein extravasation blocking and at 5-HT(1B/1D) agonist doses. Nociceptive cells with firing latencies consistent with Adelta fibres were recorded in the dorsal horn region of the trigeminal nucleus caudalis after electrical stimulation of the sagittal sinus. Both evoked (13 units) and free running (6 units) activity in cells linked to sagittal sinus stimulation were inhibited by 4991W93 delivered microiontophoretically or by intravenous administration at 10 microg/kg or 100 microg/kg, but not 0.1 microg/kg. When applied iontophoretically, 4991W93 did not appear to have an additive effect over a 5-HT(1B/1D) agonist effective concentration of zolmitriptan. These data suggest that 4991W93 is only effective at modulating the trigeminocervical complex at 5-HT(1B/1D) agonist doses. To account for neurogenic dural plasma protein extravasation blockade in animal studies, 4991W93 might have non-5-HT(1B/1D)-based pharmacological targets that are yet to be described.

Pharmacological opportunities and pitfalls in the therapy of migraine

The mild vasoconstrictor effects of modern antimigraine drugs, such as serotonin (5-HT; 5-hydroxytryptamine)1B/D agonists, have led to a search for nonvasoconstrictor approaches to therapy. Such approaches have included substance P (neurokinin I) antagonists, endothelin antagonists and highly specific 5HT1D agonists. All of these substances are effective in animal models and have no significant vasoconstrictive effects. However, all of them failed to demonstrate any antimigraine effects. Current clinical and experimental evidence therefore supports the view that isolated peripheral trigeminal nerve inhibition is insufficient to relieve acute migraine.

Substance P receptor antagonists in the therapy of migraine

Clinical observations, the vascular component of migraine pain, its pulsating or throbbing pain character, have focused attention on the trigeminal innervation of pain-sensitive intracranial structures, such as the dura mater and large vessels. These intracranial structures are innervated by the ophthalmic branch of the trigeminal nerve, which is marked by the presence of vasoactive peptides, such as substance P and calcitonin gene-related peptide. Substance P is a mediator of the sterile inflammation of the dura mater, which has been considered to be the source of migraine pain. Modern antimigraine drugs, such as 5-HT(1B/D) agonists (triptans), block this dural neurogenic inflammation dose-dependently in an animal model but their vasoconstrictor effects have led to a search for non-vasoconstrictor approaches. One such approach has been substance P (neurokinin-1) antagonists. These are highly effective in animal models of dural inflammation and have no significant vasoconstrictive effect. However, several NK(1) antagonists failed to demonstrate any effect in acute migraine. Current clinical and experimental evidence therefore supports the view that NK(1) receptor antagonists may have no significant antimigraine properties.

Discovery of 4-[3-(trans-3-dimethylaminocyclobutyl)-1H-indol-5-ylmethyl]-(4S)-oxazolidin-2-one (4991W93), a 5HT(1B/1D) receptor partial agonist and a potent inhibitor of electrically induced plasma extravasation

Utilizing a pharmacophoric model of binding of 3-(2-aminoethyl)indoles to 5HT(1B/1D) receptors, we identified the 3-aminocyclobutyl group as a potential ethylamine isostere. A novel multidimensional chemometric approach was used to predict the intrinsic activity (degree of agonism) at the receptor. A qualitative model for pharmacokinetic properties was then used to guide the synthesis toward molecules likely to have oral bioavailability in humans. A novel synthetic route to 3-(3-dimethylaminocyclobutyl)indoles was developed. Analogues showed generally lower intrinsic activity at 5HT(1B/1D) receptors than their ethylamine counterparts. 4-[3-(trans-3-Dimethylaminocyclobutyl)-1H-indol-5-ylmethyl]-(4S)-oxazolidin-2-one (4991W93, 1) was identified as a partial agonist against 5HT(1B/1D) receptors, with low intrinsic activity. This molecule also has significant activity against 5HT(1F) receptors but is selective over other 5HT receptors. In addition this compound was found to be an exceptionally potent inhibitor of electrically induced plasma extravasation. Compound 1 may have utility in the treatment and prophylaxis of migraine.

4991W93 inhibits release of calcitonin gene-related peptide in the cat but only at doses with 5HT(1B/1D) receptor agonist activity?

Calcitonin gene-related peptide (CGRP) is a marker for trigeminovascular activation and is released during the headache phase of migraine and cluster headache. CGRP may have a role in migraine through its potent cranial vasodilator effects, or by an action on trigeminal nerve activity, both of which are targeted by 5HT(1B/1D) agonist drugs. CP122,288, a conformationally restricted analogue of sumatriptan that is a potent inhibitor of neurogenic plasma protein extravasation (PPE), was ineffective at inhibiting CGRP release at a single low dose; and is also ineffective as an acute anti-migraine compound. However, it remained unclear as to whether, as a class, the conformationally-restricted triptan analogues could have inhibitory effects on CGRP in higher doses. 4991W93, a conformationally restricted analogue of zolmitriptan, is also a potent inhibitor of PPE at doses without 5HT(1B/1D)-mediated effects, that was developed as an anti-migraine drug, and thus was suitable to test whether higher doses of such conformationally restricted triptan analogues could inhibit trigeminal-evoked CGRP release. The superior sagittal sinus (SSS) was stimulated in 14 anaesthetised cats and external jugular vein blood samples were analysed by radioimmunoassay for CGRP levels before, 1 min after SSS stimulation, and 1 min after SSS stimulation in the presence of 4991W93. Stimulation of the SSS resulted in release of CGRP from the external jugular vein. 4991W93 at a dose of 0.1 and 10 microg/kg, selected for maximal PPE blocking effects in rodents, was ineffective at inhibiting CGRP release, with an SSS stimulation level of 78+/-4 pmol/l compared to a post-4991W93 level of 79+/-3 pmol/l (n=4). In comparison CGRP release was inhibited after a dose of 100 microg/kg 4991W93 from 64+/-6 to 36+/-3 pmol/l (n=5). Given that 4991W93 is inactive clinically at non-vascular doses, it seems clear that the 5HT(1B/1D) agonist effects of the compound are necessary for blockade of CGRP release and thus any anti-migraine action. Taken with the clinical results, these data emphasise the importance of CGRP release in migraine, and suggest that other non-5HT-based pharmacological targets may account for PPE blockade in animal studies.

Zolmitriptan: differences from sumatriptan

Zolmitriptan is a potent 5-HT(1B/1D) agonist whose targets include the peripheral and central components of the trigeminovascular system. It is generally well-tolerated and has dose-dependent efficacy in the treatment of migraine. The 2.5 mg dose is felt to provide the best balance between efficacy and adverse events. In a direct comparative study, the 2 h headache response rate for zolmitriptan 2.5 mg was statistically superior to sumatriptan 25 and 50 mg, although at 3.3% not clinically significant. Two comparative studies have found no difference in adverse event frequency between zolmitriptan and sumatriptan.

Inhibition of inflammation-induced thermal hypersensitivity by sumatriptan through activation of 5-HT(1B/1D) receptors

Migraine is effectively treated by drugs acting via 5-HT(1B/1D) receptors; however, the antinociceptive effects of such agents have not been fully investigated, particularly in models in which sensitization may be present. The aim of these studies was to evaluate the effects of the 5-HT(1B/1D) receptor agonist sumatriptan in specific models of pain states: a mouse model of inflammation-induced thermal hyperalgesia and a rat model of nerve injury-induced thermal hyperalgesia. In female mice, following intraplantar injection of carrageenan 225 min earlier, sumatriptan (300 microg/kg intraperitoneally; i.p.) increased paw withdrawal latency (PWL) from 3.1 +/- 0.4 s in the saline group to 5.6 +/- 0.9 s, measured 240 min postcarrageenan (P < 0.05 ANOVA followed by post hoc Dunnett's test). A similar effect was seen in male mice. Sumatriptan was also effective in male mice when given i.p. and subcutaneously 15 min precarrageenan, with a maximum effect at 30 microg/kg (i.p. latency 7.4 +/- 1.3 s compared to saline group, 2.6 +/- 0.7 s; i.v. latency 5.9 +/- 0.8 s compared to saline group, 2.9 +/- 0.3 s; P < 0.05 ANOVA followed by post hoc Dunnett's test). The number of mice required to give a response that could be reliably attributed to sumatriptan (number needed to treat) was calculated using discriminant analysis and found to be 2.6. The ability of sumatriptan to attenuate the carrageenan-induced reduction in PWL was blocked by the mixed 5-HT(1B/1D) receptor antagonist GR-127935 (3 mg/kg i.p.) but not by the 5-HT(1B) receptor antagonist SB-224289 (10 mg/kg i.p.). Sumatriptan had no effect on thermal hyperalgesia induced by sciatic nerve ligation in the rat at any time point. These data demonstrate that sumatriptan attenuates the hypersensitivity to noxious thermal stimuli induced by intraplantar carrageenan.

The pharmacology of headache

Headache is a common problem which besets most of us at some time or the other. The pharmacology of headache is complex in an overall sense but can be understood in terms of the anatomy and physiology of the pain-producing structures. Migraine can be used as a template to understand the activation of nociceptive systems in the head and thus their neurotransmitter mediation and modulation. In recent years, the role of serotonin (5-HT) in headache pharmacology has been unravelled in the context of both understanding its role in the nociceptive systems related to headache and by exploiting its 5-HT1 receptor subtypes in headache therapeutics. The pharmacology of the head pain systems, as they are known and as they might evolve, are explored in the context of both, the anatomy and physiology of trigeminovascular nociception and in the context of clinical questions, such as those of efficacy, headache recurrence and adverse events.

Triptans in migraine: a comparative review of pharmacology, pharmacokinetics and efficacy

Triptans are a new class of compounds developed for the treatment of migraine attacks. The first of the class, sumatriptan, and the newer triptans (zolmitriptan, naratriptan, rizatriptan, eletriptan, almotriptan and frovatriptan) display high agonist activity at mainly the serotonin 5-HT1B and 5-HT1D receptor subtypes. As expected for a class of compounds developed for affinity at a specific receptor, there are minor pharmacodynamic differences between the triptans. Sumatriptan has a low oral bioavailability (14%) and all the newer triptans have an improved oral bioavailability and for one, risatriptan, the rate of absorption is faster. The half-lives of naratriptan, eletriptan and, in particular, frovatriptan (26 to 30h) are longer than that of sumatriptan (2h). These pharmacokinetic improvements of the newer triptans so far seem to have only resulted in minor differences in their efficacy in migraine. Double-blind, randomised clinical trials (RCTs) comparing the different triptans and triptans with other medication should ideally be the basis for judging their place in migraine therapy. In only 15 of the 83 reported RCTs were 2 triptans compared, and in 11 trials triptans were compared with other drugs. Therefore, in all placebo-controlled randomised clinical trials, the relative efficacy of the triptans was also judged by calculating the therapeutic gain (i.e. percentage response for active minus percentage response for placebo). The mean therapeutic gain with subcutaneous sumatriptan 6mg (51%) was more than that for all other dosage forms of triptans (oral sumatriptan 100mg 32%; oral sumatriptan 50mg 29%: intranasal sumatriptan 20mg 30%; rectal sumatriptan 25mg 31%; oral zolmitriptan 2.5mg 32%; oral rizatriptan 10mg 37%; oral eletriptan 40mg 37%; oral almotriptan 12.5mg 26%). Compared with oral sumatriptan 100mg (32%), the mean therapeutic gain was higher with oral eletriptan 80mg (42%) but lower with oral naratriptan 2.5mg (22%) or oral frovatriptan 2.5mg (16%). The few direct comparative randomised clinical trials with oral triptans reveal the same picture. Recurrence of headache within 24 hours after an initial successful response occurs in 30 to 40% of sumatriptan-treated patients. Apart from naratriptan, which has a tendency towards less recurrence, there appears to be no consistent difference in recurrence rates between the newer triptans and sumatriptan. Rizatriptan with its shorter time to maximum concentration (tmax) tended to produce a quicker onset of headache relief than sumatriptan and zolmitriptan. The place of triptans compared with non-triptan drugs in migraine therapy remains to be established and further RCTs are required.

alpha-eudesmol, a P/Q-type Ca(2+) channel blocker, inhibits neurogenic vasodilation and extravasation following electrical stimulation of trigeminal ganglion

In this study, we investigated the effect of alpha-eudesmol, which potently inhibits the presynaptic omega-agatoxin IVA-sensitive (P/Q-type) Ca(2+) channel, on neurogenic inflammation following electrical stimulation of rat trigeminal ganglion. Treatment with alpha-eudesmol (0.1-1 mg/kg. i.v.) dose-dependently attenuated neurogenic vasodilation in facial skin monitored by a laser Doppler flowmetry. In addition, alpha-eudesmol (1 mg/kg. i.v.) significantly decreased dural plasma extravasation in analysis using Evans blue as a plasma marker. On the other hand, alpha-eudesmol (1 mg/kg, i.v.) did not affect mean arterial blood pressure in rats. The calcitonin gene-related peptide (CGRP) and substance P (SP) released from activated sensory nerves have recently been suggested to be associated with the neurogenic inflammation. In this study, we also showed that alpha-eudesmol (0.45-45 microM) concentration-dependently inhibits the depolarization-evoked CGRP and SP release from sensory nerve terminals in spinal cord slices. These results indicate that the anti-neurogenic inflammation action of alpha-eudesmol, which does not affect the cardiovascular system, may be due to its presynaptic inhibition of the neuropeptide release from perivascular trigeminal terminals. We also suggest that the omega-agatoxin IVA-sensitive Ca(2+) channel blocker, alpha-eudesmol, may become useful for the treatment of the neurogenic inflammation in the trigemino-vascular system such as migraine.