5-Carboxamidotryptamine is a selective agonist at 5-hydroxytryptamine receptors mediating vasodilatation and tachycardia in anaesthetized cats.
We have attempted to characterize the 5-hydroxytryptamine (5-HT) receptors mediating bronchoconstriction, vasodilatation, vasodepression and tachycardia in anaesthetized cats following bilateral vagosympathectomy and beta-adrenoceptor blockade with propranolol. 5-HT (1-100 micrograms/kg-1 i.v.) caused dose-related bronchoconstriction and tachycardia but variable and complex effects on diastolic blood pressure and carotid arterial vascular resistance. In contrast, 5-carboxamidotryptamine (5-CT; 0.01-1 micrograms kg-1 i.v.) caused consistent, dose-related decreases in diastolic blood pressure and carotid arterial vascular resistance and increases in heart rate. 5-CT did not cause bronchoconstriction. The 5-HT-induced bronchoconstriction was dose-dependently antagonized by methiothepin, methysergide and ketanserin (10-100 micrograms kg-1 i.v.). The highest doses used of these antagonists did not antagonize bronchoconstriction induced by prostaglandin F2 alpha. The high potency of all three antagonists indicate a 5-HT2-receptor mediated effect. The 5-HT- and 5-CT-induced tachycardia as well as the 5-CT-induced vasodepressor and carotid arterial vasodilator responses were dose-dependently antagonized by low doses of methiothepin (10-100 micrograms kg-1 i.v.) and by high doses of methysergide (100-1000 micrograms kg-1 i.v.) but were little affected by ketanserin in doses up to 1000 micrograms kg-1 i.v. These selective effects of 5-CT appear to be mediated by '5-HT1-like' receptors.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D007650:Ketanserin; D008297:Male; D008719:Methiothepin / Q000494:pharmacology; D008784:Methysergide / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D012701:Serotonin / Q000031:analogs & derivatives* / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*
D010880:Piperidines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D012701:Serotonin; D008719:Methiothepin; C047087:5-carboxamidotryptamine; D007650:Ketanserin; D008784:Methysergide