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PubMed1996

[Drug treatment of migraine attacks. Pharmacological considerations].

In the 1990s, the Decade of the Brain, significant progress has been made in our understanding of the pathophysiological events that take place during a migraine attack. Simultaneously, a big step forward has been made as regards drug therapy. The development of the 5-Hydroxy Tryptamine ID (5HT1D)-agonist sumatriptan has changed the lives of many migraine sufferers. This review describes attack management with analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), ergotamines and sumatriptan. Adverse events associated with ergotamines and use of sumatriptan are focused upon, with special attention to the pharmacokinetic and pharmacodynamic aspects of both these drugs. Sumatriptan has both vascular and neurogenic effects, both of which may be necessary for a good clinical outcome.

Analgesics↗
PubMed1977

[Vascular effects of adrenergic drugs and their action on intraocular pressure (author's transl)].

By means of the continuous contemporary recording of arterial blood pressure and intraocular pressure, the relationship between the two parameters was analyzed following the intravenous administration of adrenergic drugs. The aim was that of determining if during a change in systemic blood pressure the behaviour of intraocular pressure may indicate an active or passive participation to such a change. In the present studies the most important representatives of the different adrenergic groups (adrenalin, dibenamin, ergotamin, propranolol and isoproterenol) were taken in consideration. The results in normal eyes and in eyes with experimental hypertension showed that the adrenergic drugs affect the intraocular presure through a primary vasomotorial effect. An active vasodilatation of the intraocular vessels could not be demonstrated, whereas an active (adrenalin, ergotamin) as well as a passive (propranolol, isoproterenol) vasoconstriction was evidenced. The present studies allow an interpretation of the ocular hypotonizing mechanism of action of adrenergic drugs.

Animals↗
PubMed1997

[Clinical features of daily chronic headache].

INTRODUCTION: Although the International Headache Society considers chronic tension headache to be a chronic headache, patients with daily chronic headache may have pain which is not only due to tension but also has migrainous features. OBJECTIVE: To evaluate the clinical differences and abuse of drugs in a group of patients with chronic daily headache who were consecutively evaluated in the Neurology Clinic. MATERIAL AND METHODS: We consider the patients to have daily chronic headache when they have had pain at least 6 days a week for the past 6 months. Using this criterion, we studied 112 patients, of whom 90 (80.4%) were women and 22 (19.6%) men. Results. Sixty nine (61.6%) had transformed migraine and 43 (38.4%) tension headache. There were no differences in their current ages but the age of onset of the headaches varied (p = 0.000,t). Unilateral pain, trigger factors and a family history were more frequent in the cases of transformed migraine. Eighty four patients (75%) abused analgesics. Although we found different pain intensities (p = 0.000, chi 2) there was no difference in the weekly consumption of analgesics (p = 0.64, t) in the mg/week of ergotamine (p = 0.96, t) nor in absence from work between the two types of headache. CONCLUSIONS: In spite of clinical differences between transformed migraine and tension headache, which may help diagnosis, in our series abuse of analgesics (including ergotamine) was a common characteristic.

Acetaminophen↗
PubMed1976

[The use of drugs in migraine].

Drugs may be given either for treatment of the acute attack or as prophylaxis. Those most commonly used for the acute attack are analgesics, anti-emetics and ergotamine tartrate. A recent work (Volans, 1974) has shown that absorption may be impaired during a migraine attack. It is important therefore that not only is the analgesic given in an easily absorbed form but that a drug such as metaclopromide should be given to help restore the normal activity of the gastro-intestinal tract. Patients having one or more attacks of migraine a week may need prophylactic treatment. The drugs now used include: Methysergide, should only be used for severe cases when no other treatment has been found helpful. Dihydroergotamine, the vasoconstrictor activity is less than in ergotamine tartrate and can therefore be used prophylactically. Pizotifen, possesses powerful anti-serotonin properties. It also has marked antihistamine and antitryptamine properties as well as being a central sedative and anti-depressant. Clonidine, in doses of 1 mugm/Kg renders the blood vessels less sensitive to circulating amines and seems to be effective in about one third of patients with classical or common migraine. Sympathetic Blocking Agents: alpha-blockers: indoramine has recently given some good results; beta-blockers: such as propanolol and pindolol have also been used. Full trials of all the substances are now in progress. Tranquilisers and anti-depressants, two of those commonly used are diazepam and amitryptiline. In either cases a small dose only should be used. Anticonvulsants, phenytoin in doses of 50-100 mgs per day is sometimes helpful particularly in children or in those who have abnormal electroencephalograms.

Acetaminophen↗
PubMedDate not supplied

Development and validation of capillary electrophoresis methods for pharmaceutical dissolution assays.

The determination of active compounds in samples of dissolution tests of oral solid dosage forms based on the USP 23 methods was performed by capillary electrophoresis after the use of solid-phase extraction disks for the preconcentration of drugs. Enrichment factors of 20:1 allowed the determination of betamethasone and ergotamine tartrate at levels of 0.33 microgram/mL and 1.0 microgram/mL, respectively. CE analysis was performed using fused-silica capillaries (35 or 60 cm length x 75 microns i.d.) and the operating conditions consisted of 15 kV applied voltage and UV detection at 254 nm. The background electrolyte was 20-mM phosphate borate buffer, pH 9.0, containing 50 mM of sodium cholate for the separation of betamethasone and 25 mM phosphate buffer, pH 3.0, for ergotamine tartrate. Validation of the methods was also performed. Accuracy and precision of the intraday and interday assays showed comparable results with those obtained by HPLC.

Administration, Oral↗
PubMed1999

The association of the combination of sumatriptan and methysergide in myocardial infarction in a premenopausal woman.

Acute myocardial infarction occurred in a 43 year-old premenopausal woman with controlled hypertension and no known coronary artery disease following the use of the antimigraine medications sumatriptan succinate injectable form and methysergide maleate. The use of sumatriptan is contraindicated within 24 hours of using ergotamine or ergotamine-type medications such as methysergide. This contraindication is based on the theoretical possibility of prolonged vasospasm with the combined use. Methysergide is primarily a serotonin type 2 (5-HT2) antagonist, although it does act as a partial agonist at 5-HT1 receptors. It is believed that a major component of coronary artery vasospasm is possibly due to 5-HT supersensitivity mediated by 5-HT1Dbeta receptor activation. Drugs that selectively stimulate the 5-HT(D) receptors, such as sumatriptan, are potentially hazardous in people with underlying coronary artery disease, and agents with additional agonistic properties at these receptors may potentiate this effect. Physicians should be warned to inquire about prior 24-hour medication use before prescribing antimigraine medication.

Adult↗
PubMed1988

Induction of sister chromatid exchanges by ergot compounds in Chinese hamster ovary cells in vitro.

Five ergot alkaloids, d-lysergic acid derivatives, were tested for the induction of sister chromatid exchange (SCE) frequencies in cultured Chinese hamster ovary cells. The concentrations of the test substances ranged between 10(-5) and 10(-8) M. Ergotamine, ergonovine, and methylergonovine induced a significantly high number of SCEs at all the concentrations used, while with ergocristine this occurred only at the highest concentration. alpha-Ergocryptine failed to induce SCEs at any concentration. It is therefore surmised that ergotamine, ergonovine, and methylergonovine are effective inducers, ergocristine is a weak inducer, and alpha-ergocryptine is a noninducer in Chinese hamster ovary cells in vitro.

Animals↗
PubMed2006

Effects of current and prospective antimigraine drugs on the porcine isolated meningeal artery.

Vasoconstriction to agonists at serotonin (5-hydroxytryptamine; 5-HT) receptors and alpha-adrenoceptors, as well as vasodilatation induced by alpha-CGRP, have been well described in the porcine carotid circulation in vivo. The present study sets out to investigate the effects of current and prospective antimigraine drugs on porcine meningeal artery segments in vitro. Sumatriptan, ergotamine, dihydroergotamine, isometheptene and clonidine failed to contract the meningeal artery, but 5-HT, noradrenaline and phenylephrine induced concentration-dependent contractions. The contractions to 5-HT were competitively antagonized by the 5-HT(2A) receptor antagonist ketanserin, whilst those to noradrenaline were antagonized by alpha(1)-(prazosin), alpha(2)-(rauwolscine and yohimbine) and alpha(2C/2B)-(OPC-28326) adrenoceptor antagonists. Whilst dobutamine and salbutamol were ineffective, alpha-CGRP produced concentration-dependent relaxations that were antagonized by the CGRP(1) receptor antagonist olcegepant. In agreement with their lack of contractile effect, sumatriptan and ergotamine failed to influence forskolin-stimulated cyclic AMP accumulation in the porcine meningeal artery; in contrast, both compounds decreased forskolin-stimulated cyclic AMP accumulation in the human isolated saphenous vein, where they induced contractions. Finally, using RT-PCR, we could demonstrate the presence of mRNAs encoding for several 5-HT receptors (5-HT(1B), 5-HT(1D), 5-HT(1F), 5-HT(2A) and 5-HT(7)) and adrenoceptors (alpha(1A), alpha(1B), alpha(1D), alpha(2A), alpha(2B), alpha(2C), beta(1) and beta(2)), as well as that for the calcitonin receptor like receptor, a component of the CGRP(1) receptor. These results suggest that: (i) the porcine meningeal artery may not be involved in the vasoconstriction of the carotid vascular bed elicited by antimigraine drugs in anaesthetized pigs, and (ii) the mismatch between the presence of receptor mRNA and the lack of response to sumatriptan, dobutamine and salbutamol implies that mRNAs for the 5-HT(1B) receptor and beta(1)- and beta(2)-adrenoceptors are probably unstable, or that their density is too low for being translated as receptor protein in sufficient quantities.

Adrenergic alpha-Agonists↗
PubMed1999

Bovine isolated middle cerebral artery contractions to antimigraine drugs.

Ergot alkaloids, sumatriptan and the newer 5-HT1B/1D receptor agonists all contract cranial blood vessels and this effect seems to be primarily responsible for their efficacy in migraine. We have compared the contractile effects of a number of ergot and triptan derivatives on the bovine isolated middle cerebral artery and characterised the 5-hydroxytryptamine (5-HT) receptors involved by using 5-HT2A (ketanserin: 10, 30, 100 nM) and 5-HT1B/1D (GR127935: 30, 100, 300 nM) receptor antagonists. The rank order of agonist potency (pD2) was ergotamine (8.0+/-0.1) approximately dihydroergotamine (8.0+/-0.1) > avitriptan (7.4+/-0.3) >5-HT (7.0+/-0.1) > naratriptan (6.8+/-0.1) > methylergometrine (major metabolite of methysergide; 6.5+/-0.2) > rizatriptan (6.3+/-0.3) approximately zolmitriptan (6.2+/-0.1) approximately sumatriptan (6.0+/-0.2) approximately methysergide (5.9+/-0.3). The rank order of efficacy (Emax expressed as % of contraction to 100 mM K+) was 5-HT (127+/-11) > sumatriptan (56+/-5) > ergotamine (48+/-5) approximately dihydroergotamine (44+/-8) approximately methyl-ergometrine (44+/-7) > avitriptan (37+/-7) approximately rizatriptan (33+/-5) approximately methysergide (29+/-10) approximately zolmitriptan (28+/-3) approximately naratriptan (23+/-2). The concentration-response curve to 5-HT appeared to be biphasic in the presence of 100 nM ketanserin, which hardly affected sumatriptan-induced contractions, but clearly antagonised the second more efficacious phase of the curve to 5-HT. On the other hand, GR127935 caused a rightward shift of the concentration-response curves to 5-HT (in the presence of 10 microM ketanserin) and sumatriptan with pA2 values of 7.0 and 8.1, respectively. In conclusion, all acutely acting antimigraine drugs contract the bovine isolated middle cerebral artery. Whereas sumatriptan contracts the artery via the 5-HT1B/1D receptor, the 5-HT-induced contraction is mediated partly by the 5-HT2A receptor and partly by another, possibly novel receptor differing from the 5-HT1B/1D receptor. This receptor may be a target for the development of future antimigraine drugs.

Animals↗
PubMed1996

[Medical therapy for menstrual migraine].

A menstrual migraine occurs in approximately 7-10 % of women suffering from migraine. The migraine occurs from 2 days before until 3 days after the end of the menstrual period. The choice of treatment depends on the duration of the attack, which ranges from 3 to 7 days. An attack of up to 3 days duration should be treated with acetylsalicylic acid, ergotamine tartrate or naproxen, each in combination with an antiemetic (domperidone, metoclopramide). If there is no response, sumatriptan can be administered orally (25-100 mg) or subcutaneously (6 mg). In the attacks continue for more than 3 days, short-term prophylaxis with naproxen or the application of an estrogen-containing patch is indicated. Neither ovulation inhibitors nor traditional migraine prophylaxis has an influence on menstrual migraine. Patients should keep a headache diary. Short-term prophylaxis with ergotamine tartrate or tamoxifen is obsolete.

English Abstract↗
PubMed1993

The pharmacologic treatment of acute migraine headaches.

Pharmacologic agents useful in the treatment of acute migraine headaches include nonsteroidal antiinflammatory drugs (NSAIDs), ergotamines, and analgesics. Parenteral ergotamines, antiemetics, NSAIDs, corticosteroids, and sumatriptan can be successfully administered in the office or emergency room setting. In this article, evidence regarding the efficacy of these agents is reviewed.

Acute Disease↗
PubMed2004

Effects of R-102444, an orally active 5-HT2A receptor antagonist, in rat models of peripheral vascular disease.

R-102444 is a prodrug that is metabolized into R-96544, a potent and selective 5-hydroxytryptamine2A (5-HT2A) receptor antagonist. The effects of R-102444 on peripheral vascular disease were examined using two different rat models: one induced by lauric acid and the other by ergotamine plus epinephrine. R-96544 (0.3-30 nM) relaxed the 5-HT (3 microM)-precontracted rat caudal artery in a concentration-dependent manner. The intravenous administration of R-96544 (0.3-3 microg/kg) to anesthetized rats inhibited the pressor response to 5-HT (50 microg/kg i.v.) dose dependently. The oral administration of R-102444 (1 mg/kg) to rats resulted in a marked inhibition of platelet aggregation induced by 5-HT plus ADP, and statistically significant inhibition was still evident 8 h after the dosing. In contrast, sarpogrelate, at a dose of 100 mg/kg p.o., produced only a moderate antiplatelet effect. Oral administration of R-102444 (1 mg/kg/day, o.d.) significantly prevented the progression of peripheral vascular lesion induced by the injection of lauric acid into a rat femoral artery, whereas sarpogrelate (100 mg/kg/day) showed only a minimal effect. Both 5-day treatments with R-102444 (1-30 mg/kg/day p.o., o.d.), one commenced 1 h before the injection of epinephrine plus ergotamine and one just after injection, resulted in the prevention of rat tail gangrene in a dose-dependent manner, whereas sarpogrelate (100 mg/kg) produced a minimal protection in this model. Based on these results, we conclude that 5-HT2A receptor activation is involved in peripheral vascular disease in the rat and that R-102444 is a useful oral agent for the investigation of diseases involving 5-HT2A receptor activation.

Administration, Oral↗
PubMed1999

Detailed examination of fenfluramine-phentermine users with valve abnormalities identified in Fargo, North Dakota.

Although several studies have reported on valve abnormalities among users of fenfluramine or dexfenfluramine, detailed information on these subjects has not been provided, limiting the ability to understand who may be at risk for valve abnormalities and to generate hypotheses about the etiology and pathogenesis of these abnormalities. This study was a detailed medical record review of 18 previously reported users of fenfluramine and phentermine, all with valve abnormalities on echocardiogram and 2 with surgical pathology. Both clinical characteristics and medication use were recorded by trained abstracters using a standardized data collection form. Two subjects (11%) had other possible etiologies of valve disease: a history of rheumatic fever and prescribed ergotamine. Three subjects (17%) had a history of migraine headaches and 4 (22%) had murmurs noted before using fenfluramine. Use of medications that may affect serotonin receptors was common: ergotamine (1 subject, 5%), selective serotonin reuptake inhibitors (6, 33%), sumatriptan (2, 11%), and mirtazapine (1, 5%). Prior medication and nonmedication allergies were recorded in 6 (33%) and 3 (17%) subjects, respectively. All subjects had symptoms possibly due to fenfluramine or phentermine side effects. This study raises the hypotheses that valvular heart disease among fenfluramine users may be less common than previously estimated, that serotonin excess may play a role in valve pathology, and that a patient's response to anorexigens and other medications may serve as a marker for increased risk. Further study is needed to test these hypotheses.

Adult↗
PubMed2000

Cocaine metabolism in human fetal and adult liver microsomes is related to cytochrome P450 3A expression.

Cocaine N-demethylation to norcocaine was studied in human liver microsomes of different ages. Norcocaine was formed at a considerable rate in fetal (45.4+/-18.2 nmol/mg x hour, n = 8) and adult specimens (82.0+/-46.6 nmol/mg x hour, n = 15), p = 0.04 (Mann-Whitney). Furthermore, the apparent Km values in fetal specimens (0.57 and 0.48 mM, n = 2) showed a higher affinity compared with those of adults (mean value 2.7 (1.8-4.25) mM, n = 4). Estimated enzyme metabolic clearance with respect to P450 total content was higher in fetal than in adult liver microsomes (2.22 ml/nmol P450 x hour, and 0.18 (0.14-0.23) ml/nmol P450 x hour, respectively). Several drugs, known to be CYP3A substrates, were used as potential inhibitors of cocaine metabolism. Midazolam, ergotamine and erythromycin showed strong inhibition (approx. 70 %) when used at concentrations of 500 microM (midazolam, erythromycin) or 200 microM (ergotamine). The metabolism of 1 mM cocaine correlated strongly with immunodetected CYP3A protein determined by Western blotting in both fetal (r = 0.89, p = 0.19) and adult specimens (r = 0.82, p < 0.01) . These findings further support CYP3A as a major catalyst of norcocaine formation in human liver microsomes. These results are important given the potential risk of toxicity to the foetus of maternal cocaine abuse during pregnancy. Although the high Km values found in adult livers reduce the importance of this enzyme pathway in cocaine detoxication, this pathway would emerge as significant in circumstances of CYP3A induction and/or drug interactions leading to potential liver toxicity in chronic cocaine abusers.

Adolescent↗
PubMed2000

Effect of early intervention with sumatriptan on migraine pain: retrospective analyses of data from three clinical trials.

OBJECTIVE: This study assessed the efficacy of sumatriptan 50- and 100-mg tablets in the treatment of migraine attacks while the pain is mild rather than moderate/severe. BACKGROUND: Results from The Spectrum Study suggested that early treatment of migraine attacks with sumatriptan 50-mg tablets while the pain is mild might enhance pain-free response and reduce headache recurrence. METHODS: Retrospective analyses of headaches treated during mild pain were performed using data from 3 studies of sumatriptan tablets (protocols S2CM09, S2BT25, and S2BT26). Our primary interest was pain-free response 2 and 4 hours after dosing; secondary interests were use of a second dose of medication, clinical disability (as measured on a 4-point disability scale), migraine-associated symptoms, meaningful pain relief (patient defined), time to meaningful relief, sustained pain-free response, and proportion of attacks in which pain had worsened 2 and 4 hours after dosing, all of which were compared in headaches treated during mild versus moderate/severe pain. RESULTS: In S2CM09, 92 patients treated 118 headaches during mild pain. Rates of pain-free response were higher 2 hours after dosing with sumatriptan 50 mg (51%) or 100 mg (67%; P < 0.05) compared with placebo (28%), and were higher with early treatment of mild pain compared with treatment of moderate/severe pain at 2 hours (sumatriptan 50 mg: mild pain, 51%; moderate/severe pain, 31%; P < 0.05; sumatriptan 100 mg: mild pain, 67%; moderate/severe pain, 36%) and 4 hours (50 mg: 75% vs 56%; 100 mg: 90% vs 61%; P < 0.05). Early intervention also resulted in less redosing than when moderate/severe pain was treated (50 mg: 21% vs 32%; 100 mg: 20% vs 29%). More attacks treated early with sumatriptan 50 or 100 mg were associated with normal function 4 hours after dosing compared with placebo (70% and 93% vs 46%, respectively). Sustained pain-free response rates 2 to 24 hours after early dosing with sumatriptan 50 or 100 mg were also higher (34% and 53%, respectively) compared with treatment of moderate/severe pain (19% and 24%, respectively). Early treatment with sumatriptan 100 mg produced significantly higher pain-free rates at 2 hours after dosing (P < 0.001) than did ergotamine plus caffeine (S2BT25: 69% vs 34%, respectively) or aspirin plus metoclopramide (S2BT26: 73% vs 25%, respectively). CONCLUSIONS: Sumatriptan 50- and 100-mg tablets are effective whether pain is mild or moderate/severe. However, treatment with sumatriptan while pain is mild provides high pain-free response rates while reducing the need for redosing, benefits not seen with ergotamine plus caffeine or aspirin plus metoclopramide.

Dose-Response Relationship, Drug↗
PubMed2004

French guidelines for the diagnosis and management of migraine in adults and children.

BACKGROUND: The French Recommendations for Clinical Practice: Diagnosis and Therapy of Migraine are guidelines concerning the overall management of patients with migraine, including diagnostic and therapeutic strategies and assessment of disability. OBJECTIVE: This article summarizes the guidelines as they apply to adults and children, and proposes future direction for steps toward optimal treatment of migraine in patients in France. METHODS: The recommendations were categorized into 3 levels of proof (A-C) according to the National Agency for Accreditation and Evaluation in Health (ANAES) methodology and were based on a professional consensus reached among members of the Working Group and the Guidelines Review Group of the ANAES. RESULTS: The International Headache Society diagnostic criteria for migraine should be used in routine clinical practice. Recommended agents for the treatment of migraine in adults include nonsteroidal anti-inflammatory drugs, acetylsalicylic acid (ASA) monotherapy or in combination with metoclopramide, acetaminophen monotherapy, triptans, ergotamine tartrate, and dihydroergotamine mesylate. Patients should use the medication as early as possible after the onset of migraine headache. For migraine prophylaxis in adults, the following can be used: propranolol, metoprolol, oxetorone, or amitriptyline as first-line treatment, and pizotifen, flunarizine, valproate sodium, or topiramate as second-line treatment. Migraine in children can be distinguished from that in adults by shorter duration (2-48 hours in children aged <15 years), more frequent bilateral localization, frequent predominant gastrointestinal disturbances, and frequent pallor hailing the onset of the attack. The following drugs are recommended in children and adolescents: ibuprofen in children aged >6 months, diclofenac in children weighing >16 kg, naproxen in children aged >6 years or weighing >25 kg, ASA alone or in combination with metoclopramide, acetaminophen alone or in combination with metoclopramide, and ergotamine tartrate in children aged >10 years. CONCLUSIONS: These guidelines are intended to help general practitioners to manage migraine patients according to the rules of evidence-based medicine.

Adolescent↗
PubMedDate not supplied

The effects of cyclic 3',5'-AMP on the lysosomes of newborn rat hepatocytes.

Certain effects of cyclic 3',5'-AMP administration on the lysosomes of newborn rat hepatocytes were studied using biochemical assays, electron microscopy, and quantitative morphometry. Cyclic AMP produced accelerations of postnatal hyaloplasmic glycogen breakdown and lysosomal glycogen breakdown, and an increase in activity of the lysosomal enzyme acid alpha-1,4-glucosidase (maltase). Ergotamine, a known antagonist of the effects of cyclic AMP, produced inhibitions of postnatal hyaloplasmic glycogen breakdown and lysosomal glycogen breakdown. Cyclic AMP increased while ergotamine decreased the volume of lysosomes. The results support the postulate that the catabolism of lysosomal glycogen is controlled by those agents that regulate the catabolism of hyaloplasmic glycogen (O. B. Kotoulas and M. J. Phillips, Amer. J. Pathol. (1971) 63, 1-17; O. B. Kotoulas et al., Amer. J. Pathol. (1971) 63, 23-36). Control is mediated by changes in the activity of the lysosomal enzyme acid alpha-1,4-glucosidase. Lysosomes actively participate in the degradation of hepatocellular glycogen.

Animals↗
PubMed1997

Characterization of putative 5-HT7 receptors mediating tachycardia in the cat.

1. It has been suggested that the tachycardic response to 5-hydroxytryptamine (5-HT) in the spinal-transected cat is mediated by '5-HT1-like' receptors since this effect, being mimicked by 5-carboxamidotryptamine (5-CT), is not modified by ketanserin or MDL 72222, but it is blocked by methiothepin, methysergide or mesulergine. The present study was set out to reanalyse this suggestion in terms of the IUPHAR 5-HT receptor classification schemes proposed in 1994 and 1996. 2. Intravenous (i.v.) bolus injections of the tryptamine derivatives, 5-CT (0.01, 0.03, 0.1, 0.3, 1, 3, 10 and 30 microg kg(-1)), 5-HT (3, 10 and 30 microg kg(-1)) and 5-methoxytryptamine (3, 10 and 30 microg kg(-1)) as well as the atypical antipsychotic drug, clozapine (1000 and 3000 microg kg(-1)) resulted in dose-dependent increases in heart rate, with a rank order of agonist potency of 5-CT >> 5-HT > 5-methoxytryptamine >> clozapine. 3. The tachycardic effects of 5-HT and 5-methoxytryptamine were dose-dependently antagonized by i.v. administration of lisuride (30 and 100 microg kg(-1)), ergotamine (100 and 300 microg kg(-1)) or mesulergine (100, 300 and 1000 microg kg(-1)); the highest doses of these antagonists used also blocked the tachycardic effects of 5-CT. Clozapine (1000 and 3000 microg kg(-1)) did not affect the 5-HT-induced tachycardia, but attenuated, with its highest dose, the responses to 5-methoxytryptamine and 5-CT. However, these doses of clozapine as well as the high doses of ergotamine (300 microg kg(-1)) and mesulergine (300 and 1000 microg kg(-1)) also attenuated the tachycardic effects of isoprenaline. In contrast, 5-HT-, 5-methoxytryptamine- and 5-CT-induced tachycardia were not significantly modified after i.v. administration of physiological saline (0.1 and 0.3 ml kg(-1)), the 5-HT(1B/1D) receptor antagonist, GR127935 (500 microg kg(-1)) or the 5-HT(3/4) receptor antagonist, tropisetron (3000 microg kg(-1)). 4. Intravenous injections of the 5-HT1 receptor agonists, sumatriptan (30, 100 and 300 microg kg(-1)) and indorenate (300 and 1000 microg kg(-1)) or the 5-HT4 receptor (partial) agonist cisapride (300 and 1000 microg kg(-1)) were devoid of effects on feline heart rate per se and failed to modify significantly 5-HT-induced tachycardic responses. 5. Based upon the above rank order of agonist potency, the failure of sumatriptan, indorenate or cisapride to produce cardioacceleration and the blockade by a series of drugs showing high affinity for the cloned 5-ht7 receptor, the present results indicate that the 5-HT receptor mediating tachycardia in the cat is operationally similar to other putative 5-HT7 receptors mediating vascular and non-vascular responses (e.g. relaxation of the rabbit femoral vein, canine external carotid and coronary arteries, rat systemic vasculature and guinea-pig ileum). Since these responses represent functional correlates of the 5-ht7 gene product, the 5-HT7 receptor appellation is reinforced. Therefore, the present experimental model, which is not complicated by the presence of other 5-HT receptors, can be utilized to characterize and develop new drugs with potential agonist and antagonist properties at functional 5-HT7 receptors.

5-Methoxytryptamine↗