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PubMed1995

Characterization and distribution of putative 5-ht7 receptors in guinea-pig brain.

1. In the presence of (-)-cyanopindolol (1.0 microM) and sumatriptan (1.0 microM), 0.5 nM [3H]-carboxamidotrytamine ([3H]-5-CT) labelled a single population of receptors in guinea-pig cerebral cortex membranes. 2. 5-HT-displaceable binding was rapid, saturable and reversible. A high affinity binding site was characterized both by equilibrium saturation (Kd = 0.76 +/- 0.28 nM; Bmax = 68.1 +/- 26.7 fmol mg-1 protein) and kinetic (Kd = 0.18 +/- 0.05 nM) analysis. The pharmacological profile of this site was similar to the profile obtained in transfected CHO-K1 cells expressing guinea-pig 5-ht7 receptors. 3. Autoradiographic analysis revealed a discrete localization of binding sites in guinea-pig brain, with the highest density of sites in the medial thalamic nuclei and related limbic and cortical regions. Moderate levels of binding were detected in sensory relay nuclei, substantia nigra, hypothalamus, central grey and dorsal raphe nuclei. This distribution corresponded to that observed using in situ hybridization with [35S]-UTP labelled riboprobes complementary to mRNA encoding the guinea-pig 5-ht7 receptor. 4. In conclusion, under appropriate conditions, [3H]-5-CT labelled a single population of saturable binding sites that corresponded to an endogenous 5-ht7 receptor in guinea-pig brain. The distribution of 5-ht7 receptors in thalamocortical and limbic brain regions suggests a role for these receptors in sensory and affective behaviours.

Animals↗
PubMed1996

Characterization of putative 5-ht7 receptors mediating direct relaxation in Cynomolgus monkey isolated jugular vein.

1. 5-Hydroxytryptamine (5-HT) receptors mediating contraction and relaxation are present in Cynomolgus monkey isolated jugular vein denuded of endothelium. 2. In the absence of spasmogen, alpha-methyl-5-HT and sumatriptan contracted the tissues with potency values (pEC50) of 6.8 (n = 2) and 6.4 +/- 0.1 (mean +/- s.e. mean, n = 3), respectively. In contrast, 5-HT caused an initial contraction (10 nM - 1 microM), followed by relaxation (1 microM - 32 microM). The contractile effect of alpha-methyl-5-HT was antagonized by ketanserin with a pKB value of 8.1 (n = 2). 5-Carboxamidotryptamine (5-CT), 5-methoxytryptamine (5-MeOT) and 8-OH-DPAT did not contract or relax the tissues in the absence of spasmogen. 3. In tissues precontracted with U46619 (10 nM) and in the presence of 5-HT1A, 5-HT1B, 5-HT2A, 5-HT3, and 5-HT4 receptor blockade, 5-CT and 5-MeOT caused endothelium-independent relaxation with potency values of 7.5 +/- 0.1 (n = 21) and 5.7 +/- 0.1 (n = 4), respectively. The potency of 5-HT was 7.2 (n = 2) while alpha-methyl-5-HT did not start to relax the tissues below a concentration of 10 microM. 4. Relaxations elicited by 5-CT were antagonized by the following compounds (with pKB values in parentheses): methiothepin (9.7), mesulergine (8.1), metergoline (8.0), clozapine (7.8), mianserin (7.7), spiperone (7.3), ritanserin (7.1), methysergide (7.0) and ketanserin (5.7). 5. It is concluded that the 5-HT receptor mediating endothelium-independent relaxation may be a functional correlate of the putative 5-ht7 receptor.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1996

Functional, endogenously expressed 5-hydroxytryptamine 5-ht7 receptors in human vascular smooth muscle cells.

Human uterine artery smooth muscle cells in culture were shown to express constitutively both 5-ht7 receptor mRNA and 5-ht7-like receptors functionally linked to cyclic AMP formation. 5-Carboxamidotryptamine (5-CT) and 5-HT enhanced forskolin-stimulated cyclic AMP accumulation in these cells, with pEC50 values of 7.12 and 6.25, sumatriptan being very weakly active. Both methiothepin (0.1 microM) and clozapine (1 microM), but not the 5-HT4-receptor antagonist, SDZ 205-557 (10 microM) antagonized the effects of 5-CT. In reverse transcriptase-polymerase chain reaction analysis, the mRNA for 5-ht7, but not for 5-HT4 or 5-ht6 receptors was found to be strongly expressed in the same cells. These findings represent a further step toward the recognition of 5-ht7 receptors as real, functional receptors.

Cells, Cultured↗
PubMed1996

Characterization of a 5-HT1B receptor on CHO cells: functional responses in the absence of radioligand binding.

1. Chinese hamster ovary (CHO) cells have been reported to be devoid of 5-HT receptors and have frequently been used as hosts for the expression of cloned 5-HT receptors. Unexpectedly, 5-HT was found to induce profound inhibition of forskolin-stimulated cyclic AMP production in these cells and the aim of this study was to classify the 5-HT receptor involved. 2. In CHO(dhfr-) cells 5-HT was a potent agonist and caused 80-100% inhibition of forskolin stimulated cyclic AMP production. A study using several 5-HT1 receptor agonists revealed the following potencies (p[A50]): RU24969 (9.09 +/- 0.17) > 5-carboxamidotryptamine (8.86 +/- 0.20) > 5-HT (8.07 +/- 0.05) > CP-93,129 (7.74 +/- 0.10) > sumatriptan (5.93 +/- 0.04). All five agonists achieved a similar maximum effect. Irreversible receptor alkylation studies yielded a pKA estimate of 7.04 +/- 0.34 for 5-HT. 3. The 5-HT1A/1B antagonist, (+/-)-cyanopindolol (4-100 nM), caused parallel rightward shifts of the 5-HT concentration-effect curve with no change in asymptote. Schild analysis yielded a pKB estimate of 8.69 +/- 0.09 (Schild slope 1.13 +/- 0.10). (+/-)-Cyanopindolol actually behaved as a partial agonist with an intrinsic activity of 0.2-0.5 and a p[A50] of 8.55. 4. 5-HT (0.01-10 microM) also elicited a concentration-dependent increase in intracellular [Ca2+] in CHO(dhfr-) cells thus demonstrating that dual coupling is not a phenomenon restricted to systems in which there is overexpression of transfected receptors. 5. This agonist and antagonist profile is consistent with the presence of a 5-HT1B receptor. 8-OH-DPAT (1 microM) and renzapride (3 microM) were without effect on forskolin-stimulated cyclic AMP production and ketanserin (0.3 microM) did not antagonize the inhibition produced by 5-HT, thus excluding the involvement of 5-HT1A, 5-HT4, and 5-HT2 receptors. 6. The possibility that expression of a 5-HT1B receptor was associated with the dhfr- mutation was excluded since RU24969, 5-HT and CP-93,129 were also potent agonists in unmutated, CHO-K1 cells: p[A50] 9.03 +/- 0.03, 8.34 +/- 0.05, 7.69 +/- 0.07 respectively, and (+/-)-cyanopindolol (0.1 microM) shifted the 5-HT curve to the right and yielded a pA2 estimate of 8.70 +/- 0.06. 7. Little or no specific binding of [3H]-5-HT (0.1-200 nM) or of the high affinity ligand [125I]-iodocyanopindolol (0.01-3 nM) to CHO(dhfr-) cell membranes could be detected. 5-HT also failed to elicit any increase in the binding of [35S]-GTP gamma S to CHO membranes. 8. In conclusion, cultured CHO cells express 5-HT1B receptors which are negatively coupled to adenylyl cyclase and positively coupled to increases in intracellular calcium. The absence of radioligand binding was unexpected in view of the high potency of 5-HT and the partial agonist activity of the normally 'silent' competitive antagonist, (+/-)-cyanopindolol. This implies very efficient receptor-effector coupling of a low density of 5-HT1B receptors. Clearly, the absence of detectable radioligand binding cannot be assumed to mean the absence of receptors capable of eliciting a significant functional response.

Animals↗
PubMed1992

SUNCT may be another manifestation of orbital venous vasculitis.

A patient with more than 20 years of SUNCT, i.e., long lasting periods with frequent attacks of intense orbital pain with a duration of about one minute, associated with ipsilateral conjunctival injection, lacrimation, rhinorrhea and facial sweating is described. Some attacks were possibly related to increased cerebral blood flow but could also be triggered from the oral area. Orbital phlebography showed pathologic changes on the side of the pain, changes which were normalized when these attacks ceased to appear. Due to these findings in conjunction with serum evidence of inflammation, associated systemic symptoms and susceptibility to steroids and azathioprine, venous vasculitis is suggested to be the cause of SUNCT in this patient. Carbamazepine and sumatriptan decreased the frequency, intensity and duration of attacks, although not completely.

Headache↗
PubMedDate not supplied

Application of metoclopramide specificity in migraine attacks therapy.

The 5-HT3 antagonism property of metoclopramide, acting on receptors presumably located in the trigeminovascular system, is the theoretical basis of its remarkable success, as a single intravenous agent, in the treatment of migraine attacks. The specific anti-migraine activity of oral metoclopramide is, most probably, applicable only when its plasma level is equivalent to 10 mg injected intravenously. The clinical effective dose of ergotamine, beginning from the minimal dose of 1 mg, correlates well with its affinity for 5-HT1B and 5-HT1D receptors, and the rank order of clinical potency of ergotamine is superior to sumatriptan. The presumed synergic power of drugs that interact with both 5-HT1 and 5-HT3 receptors is examined, in order to formulate a highly potent, low headache recurrence, oral combination.

Caffeine↗
PubMed1995

Provocation of unilateral pain in cluster headache patients by breathing CO2.

Ten patients with cluster headache in an active period and 6 controls were studied as to heart rate, blood pressure, blood flow in the common carotid arteries (CCA), end-tidal PCO2 and pain before, during and after 6 minutes of breathing 6% CO2 in air. Heart rate increased significantly during CO2 breathing in controls but not in patients. The cluster headache patients had significantly lower baseline end-tidal PCO2 than controls. CCA blood flow increased significantly during CO2 breathing in both groups. Vascular resistance decreased during CO2 provocation and increased above baseline levels 5 minutes after provocation in both groups and related to the end-tidal PCO2. Six of eight cluster headache patients, who had an increase of blood flow at provocation, reported slight to moderate unilateral pain in relation to the CO2 provocation in contrast to controls. One patient treated with 6 mg sumatriptan 2.5 hours before the provocation had an end-tidal PCO2 within the range of the controls, and did not get an increase of CCA blood flow or pain at provocation. Six of the cluster headache patients were restudied when out of the active period. There was still no heart rate increase during CO2 breathing and end-tidal PCO2 was still lower than in the controls. Unilateral headache was not provoked.

Administration, Inhalation↗
PubMed2004

Cost considerations of acute migraine treatment.

OBJECTIVE: To provide medication price data and cost-reducing strategies for the acute treatment of migraine. METHODS: Retail prices for common acute care medications were found at http://www.drugstore.com. Cost-reduction tactics were obtained from literature searches and clinical experience. RESULTS: Several strategies can reduce cost without sacrificing treatment outcome. In mild to moderate migraine, low-priced nonsteroidal anti-inflammatory drugs can be used as first-line medications due to their proven efficacy and favorable tolerability. For patients with more severe migraine, implementing a stratified care approach-using migraine-specific medications early in acute treatment-is cost-effective for most patients. Stratified care not only improves outcome and decreases disability, but also reduces cost. Pill splitting and early administration of triptans within an attack enhance their value. Supplying rescue medications, such as opioids, sedatives, and phenothiazines, can prevent emergency department visits. Minimizing multiple dosing of triptans and reducing utilization of expensive health care resources are key factors in reducing the cost of effective migraine treatment. An important affordability factor for patients with co-payments is the number of triptan pills per package. Sumatriptan, naratriptan, and frovatriptan each contain 9 tablets per package, while most other triptan packages contain 6. Current triptan retail prices (per unit) include: Amerge 1 and 2.5 mg, 17.78 dollars; Axert 6.25 and 12.5 mg, 16.31 dollars; Frova 2.5 mg, 13.89 dollars; Imitrex 50 mg, 14.96 dollars; Imitrex 100 mg, 14.41 dollars; Imitrex Nasal Spray 20 mg, 21.61 dollars; Imitrex SQ 6 mg, 50.26 dollars; Maxalt 5 and 10 mg, 15 dollars; Maxalt-MLT 5 and 10 mg, 15 dollars; Relpax 40 mg, 13.58 dollars; Zomig 2.5 mg, 13.67 dollars; Zomig 5 mg, 15.89 dollars; Zomig-ZMT 2.5 mg, 13.67 dollars; and Zomig-ZMT 5 mg, 15.89 dollars. CONCLUSIONS: Practitioners can optimize the use of health care dollars without compromising quality of care through awareness of cost-saving treatment strategies, as well as price variations among medications.

Acute Disease↗
PubMed2004

Frovatriptan use in migraineurs with or at high risk of coronary artery disease.

OBJECTIVE: To investigate the cardiovascular effects of frovatriptan 2.5 mg during a migraine attack in patients with, or at high risk of, coronary artery disease. BACKGROUND: Rare occurrences of myocardial ischemia and coronary and peripheral vasospasm associated with the use of sumatriptan have triggered concern over the vasoconstrictor properties of the triptan class of drugs. METHODS: This randomized, double-blind, placebo-controlled, parallel-group study was conducted in 14 US private headache referral centers or clinics. Seventy-five patients, aged 18 years and older, with a history of migraine who were at high risk (Framingham score > or =14) of or who had previously documented coronary artery disease were evaluated. RESULTS: Incidence of clinically significant electrocardiogram changes was higher at all time points postdose with placebo than with frovatriptan, reaching statistical significance at 4 hours (40% versus 19%, P=.026). Similar proportions of patients had ischemia documented on Holter monitoring in the placebo (13%) and frovatriptan (11%) groups, and the incidence of arrhythmias was higher in the placebo group (11% versus 3%). There were no clinically significant changes in heart rate or blood pressure in either group. Adverse event profiles were similar for placebo and frovatriptan. CONCLUSIONS: In this exploratory study of migraineurs with, or at high risk of, coronary artery disease, frovatriptan 2.5 mg was well tolerated and not associated with an increase in cardiovascular monitoring abnormalities.

Adolescent↗
PubMed2004

Cardiovascular tolerability and safety of triptans: a review of clinical data.

Triptans are not widely used in clinical practice despite their well-established efficacy, endorsement by the US Headache Consortium, and the demonstrable need to employ effective intervention to reduce migraine-associated disability. Although the relatively restricted use of triptans may be attributed to several factors, research suggests that prescribers' concerns about cardiovascular safety prominently figure in limiting their use. This article reviews clinical data--including results of clinical trials, postmarketing studies and surveillance, and pharmacodynamic studies--relevant to assessing the cardiovascular safety profile of the triptans. These data demonstrate that triptans are generally well tolerated. Chest symptoms occurring during use of triptans are usually nonserious and usually not attributed to ischemia. Incidence of triptan-associated serious cardiovascular adverse events in both clinical trials and clinical practice appears to be extremely low. When they do occur, serious cardiovascular events have most often been reported in patients at significant cardiovascular risk or in those with overt cardiovascular disease. Adverse cardiovascular events also have occurred, however, in patients without evidence of cardiovascular disease. Several lines of evidence suggest that nonischemic mechanisms are responsible for sumatriptan-associated chest symptoms, although the mechanism of chest symptoms has not been determined to date. Importantly, most of the clinical trials and clinical practice data on triptans are derived from patients without known cardiovascular disease. Therefore, the conclusions of this review cannot be extended to patients with cardiovascular disease. The cardiovascular safety profile of triptans favors their use in the absence of contraindications.

Chest Pain↗
PubMedDate not supplied

Individualizing treatment with verapamil for cluster headache patients.

BACKGROUND: Verapamil is currently the best available prophylactic drug for patients experiencing cluster headaches (CHs). Published papers usually state 240 to 480 mg taken in three divided doses give good results, ranging from 50% to 80%; others mention higher doses--720, even 1200 mg per day. In clinical practice we found we needed to adapt dosage to individual's time of attacks, in particular giving higher doses before going to bed to suppress severe nocturnal episodes. A few only required 120 mg daily. We therefore evolved a scheme for steady and progressive drug increase until satisfactory control had been achieved. OBJECTIVE: To find the minimum dose of verapamil required to prevent episodic and chronic cluster headaches by supervising each individual and adjusting the dosage accordingly. METHODS: Consecutive patients with episodic or chronic CH (satisfying International Headache Society (IHS) criteria) were started on verapamil 40 mg in the morning, 80 mg early afternoon, and 80 mg before going to bed. Patients kept a diary of all attacks, recording times of onset, duration, and severity. They were advised, verbally and in writing, to add 40 mg verapamil on alternate days, depending on their attack timing: with nocturnal episodes the first increase was the evening dose and next the afternoon one; when attacks occurred on or soon after waking, we advised setting an alarm clock 2 hours before the usual waking time and then taking the medication. Patients were followed-up at weekly intervals until attacks were controlled. They were also reviewed when a cluster period had ended, and advised to continue on the same dose for a further 2 weeks before starting systematic reduction. Chronic cluster patients were reviewed as often as necessary. RESULTS: Seventy consecutive patients, 52 with episodic CH during cluster periods and 18 with chronic CH, were all treated with verapamil as above. Complete relief from headaches was obtained in 49 (94%) of 52 with episodic, and 10 (55%) of 18 with chronic CH; the majority needed 200 to 480 mg, but 9 in the episodic, and 3 in the chronic group, needed 520 to 960 mg for control. Ten, 2 in the episodic and 8 in the chronic group, with incomplete relief, required additional therapy-lithium, sumatriptan, or sodium valproate. One patient withdrew because verapamil made her too tired, another developed Stevens-Johnson syndrome, and the drug was withdrawn. CONCLUSIONS: Providing the dosage for each individual is adequate, preventing CH with verapamil is highly effective, taken three (occasionally with higher doses, four) times a day. In the majority (94%) with episodic CH steady dose increase under supervision, totally suppressed attacks. However in the chronic variety only 55% were completely relieved, 69% men, but only 20% women. In both groups, for those with partial attack suppression, additional prophylactic drugs or acute treatment was necessary.

Adult↗
PubMed2005

Triptan nonresponder studies: implications for clinical practice.

The maximum absolute response rate with oral triptans, as measured in clinical trials by the incidence of relief from migraine pain at 2 hours after taking medication, is approximately 70%. Therefore around 30% of patients fail to respond to a particular triptan. Nonresponse is likely to be due to a variety of factors, including low and inconsistent absorption, use of the medication late in an attack, inadequate dosing, and variability in individual response. Evidence from recent clinical trials, however, confirms the common clinical observation that patients with a poor response to one triptan can benefit from subsequent treatment with a different triptan. Two-hour pain-relief rates of 25% to 81% using alternative triptans (naratriptan, almotriptan, eletriptan, zolmitriptan, and rizatriptan) have been reported in patients who were described as poor responders to sumatriptan. Physicians should remain vigilant in assessing the response to acute therapy and take advantage of simple clinical questionnaires that have been developed to facilitate the recognition of those patients who require and may benefit from a change in acute therapy.

Acute Disease↗
PubMed2006

Calcitonin gene-related peptide (CGRP) and migraine.

The neuropeptide calcitonin gene-related peptide (CGRP) has long been postulated to play an integral role in the pathophysiology of migraine. While clinical findings are consistent with such a role, the specific pathogenic mechanisms of CGRP in migraine have remained speculative until recently. Through advances in molecular neuroscience, the pathogenic mechanisms of CGRP in migraine have begun to be elucidated. This paper discusses the hypothesized role of CGRP in migraine and reviews recent findings on the molecular mechanisms of this neuropeptide in migraine pathophysiology. Studies in cultured trigeminal neurons demonstrate that CGRP is released from trigeminal ganglia cells, that CGRP transcription is increased under conditions mimicking neurogenic inflammation, that migraine pharmacotherapies can both reduce CGRP release and inhibit CGRP transcription, and that tumor necrosis factor-alpha (TNF-alpha), an endogenous inflammatory mediator implicated in migraine, can stimulate CGRP transcription. Together, the results suggest that, in migraine, activation of trigeminal nerves release CGRP and other peptides that cause the release of proinflammatory mediators. These mediators further increase CGRP synthesis and release over hours to days in correspondence with the 4- to 72-hour duration of a typical migraine episode. The increased CGRP synthesis and release might be mediated by activation of mitogen-activated protein kinase pathways, which, in turn, can be modulated by endogenous inflammatory substances such as TNF-alpha and affected by drugs such as sumatriptan.

Animals↗
PubMed2006

Nasal delivery of antimigraine drugs: clinical rationale and evidence base.

The intranasal route of administration for antimigraine drugs offers many theoretical and practical advantages. A drug that is administered intranasally is absorbed by the highly vascular mucous membranes of the nose, which allows for rapid delivery of un-metabolized drug to the central nervous system. The onset of action is thus considerably earlier than with oral administration requiring gastrointestinal absorption. The intranasal route also provides several practical advantages, such as greater acceptability to patients because of the noninvasive mode of delivery, the ability to take medication when severe nausea or vomiting is present, and a better adverse event profile. Three antimigraine drugs are available in intranasal formulation: dihydroergotamine, sumatriptan, and zolmitriptan. This article reviews the pharmacology, efficacy, safety, and tolerability of these agents. All are well tolerated by patients and have demonstrated efficacy in the treatment of migraine headache. Each of these drugs has a unique pharmacokinetic and pharmacodynamic profile, which may support a clinical preference for one intranasal agent over another in treating patients with specific headache features.

Administration, Intranasal↗
PubMed2005

Clinical data on the CGRP antagonist BIBN4096BS for treatment of migraine attacks.

Basal studies have shown that calcitonin gene-related peptide (CGRP) is a major sensory neuronal messenger in the trigeminovascular system, the pathway conveying intracranial pain. In migraine and cluster headache attacks, CGRP is released in parallel with the pain and successful treatment of the attacks abort both the associated pain and the CGRP release. The search for a potent small molecule CGRP antagonist has been successful and such an agent has been tested in preclinical and clinical studies. The aim of the present study was to examine current knowledge on the clinical pharmacology of systemic BIBN4096BS, which has been shown in man to abort acute migraine attacks as well or better than oral sumatriptan. BIBN4096BS is a specific and potent CGRP receptor antagonist in humans. In safety and tolerability studies the substance is well tolerated with no or only mild side effects. In acute migraine attacks the overall response was 66% with the drug and 27% with placebo. A difference as compared to placebo was seen at 30 min; the response was still rising at 4 h suggesting a long duration of action. At 24 h the pain-free rate was better than that with triptans, suggesting a lower grade of rebound and perhaps even a prophylactic possibility.

Calcitonin Gene-Related Peptide↗
PubMed1994

Migraine--diagnosis and pathophysiology.

The new classification of headaches will be briefly described. The main primary headaches are migraine with and without aura, tension-type headache and cluster headache. The operational diagnostic criteria for migraine with aura, migraine without aura and episodic tension-type headache will be presented. After this the clinical pictures of migraine with aura (previously classic migraine) and migraine without aura (previously common migraine) will be described. At last the current concepts concerning pathophysiology, regional cerebral blood flow changes, changes in extra- and intracranial arteries and mechanisms of action of ergotamine and sumatriptan will be presented.

Humans↗
PubMed1998

Genetic variation in human 5-HT receptors: potential pathogenetic and pharmacological role.

Mutation screening identified variants of h5-HT1A (Gly-22-Ser, Ile-28-Val, Arg-219-Leu), h5-HT1B (Phe-124-Cys), h5-HT2A (Thr-25-Asn, His-452-Tyr), h5-HT2C (Cys-23-Ser) and h5-HT7 (Thr-92-Lys, Pro-279-Leu) receptors. Screening of h5-HT1D, h5-ht1e, h5-ht1f and h5-ht5 receptor genes failed to detect any significant mutations. No differences in radioligand binding properties were observed between the h5-HT1A Ile-28-Val variant receptor (VR) and the wildtype receptor (WTR). Binding profiles of the h5-HT1A Gly-22-Val variant and the WTR were also very similar, but the 8-OH-DPAT-induced down-regulation and desensitization of the VR was attenuated. The h5-HT1B Phe-124-Cys variant leads to considerable changes in [3H]5-carboxamidotryptamine binding: Bmax was decreased and the affinity of various h5-HT1B ligands was modified (usually increased; e.g., in the case of sumatriptan). The h5-HT2A His-452-Tyr variant causes an alteration of the amplitude and timing of intracellular calcium mobilization in platelets from 452-His/452-Tyr heterozygous compared to 452-His/452-His homozygous individuals. Most, but not all, of the VRs listed above were examined for association with, e.g., bipolar depression and schizophrenia, yet no relation was observed. The most consistent finding was an association between a silent mutation (102T/C) in the h5-HT2A receptor gene and schizophrenia; this association may be explained by linkage disequilibrium with a functional variant in the regulatory region of the gene. Studies of the therapeutic response to clozapine produced no homogeneous results with respect to the pharmacogenetic significance of the various mutations in the h5-HT2A and h5-HT2C receptor genes.

Bipolar Disorder↗
PubMed1996

Endogenous monoamines inhibit glutamate transmission in the spinal trigeminal nucleus of the guinea-pig.

1. With the use of whole-cell patch clamp recordings in slices of guinea-pig substantia gelatinosa (SG), we studied the serotonin (5-HT)- and noradrenaline (NA)-mediated inhibition of glutamate-mediated EPSCs evoked from primary afferent stimulation. 2. The frequency of spontaneous EPSPs was reduced by 5-HT and NA. 3. The inhibition of EPSCs caused by 5-HT was mediated by the 5-HT1D receptor subtype, since the 5-HT1D agonist, sumatriptan (1 microM), was effective. 4. NA and the alpha 2-agonist, 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK 14304), decreased the EPSCs and this inhibition was blocked by the alpha 2-antagonists, idazoxan (1 microM) and yohimbine (1 microM). 5. The 5-HT-releasing agent, fenfluramine (10 microM), and the Na-releasing agent, amphetamine (1 microM), also depressed EPSCs. Pretreatment of slices with the 5-HT-depleting agent, p-chloro-amphetamine (10 microM), attenuated the inhibition of fenfluramine but failed to antagonize the effects of exogenously applied 5-HT. 6. These in vitro results suggest that presynaptic inhibition of glutamate release from primary afferents can provide another mechanism to explain the antinociceptive effects of 5-HT and NA obtained in vivo.

Adrenergic alpha-2 Receptor Agonists↗