Analysis of the contractile effect of 5-hydroxytryptamine on the isolated posterior communicating artery of the cat.
5-Hydroxytryptamine (5-HT) induced dose-dependent increases in tension on the isolated posterior communicating artery (PCA) of the cat were significantly antagonized by lysergic acid diethylamide (LSD, 6 X 10(-9). In the presence of the phentolamine (10(-6) M) the contraction induced by the two lowest doses of 5-HT was significantly reduced. Pretreatment of the animals with reserpine (3 mg kg-1, i.p., total dose) did not modify the dose-response curve to 5-HT except for the lowest dose. Removal of both superior cervical sympathetic ganglia 15 days before the experiment brought about a significant increase in the vasoconstriction induced by 5-HT at all the doses compared with the control. Cocaine (10(-6) M) induced a significant shift to the left of the dose-response curve to 5-HT but the maximum response was the same as in the control. The augmented response to 5-HT after denervation was partially antagonized by LSD (6 X 10(-9) M) but not by phentolamine (10(-6) M). These results show that the vasoconstriction elicited by 5-HT in the PCA of the cat is mainly due to direct stimulation of tryptaminergic receptors. The participation of an indirect adrenergic component in the contractile effects of 5-HT seems to be negligible.
D000818:Animals; D002415:Cats; D002536:Cerebral Arteries / Q000187:drug effects*; D003042:Cocaine / Q000494:pharmacology; D004347:Drug Interactions; D005260:Female; D066298:In Vitro Techniques; D008238:Lysergic Acid Diethylamide / Q000494:pharmacology; D008297:Male; D009121:Muscle Denervation; D010646:Phentolamine / Q000494:pharmacology; D012110:Reserpine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects*
D012701:Serotonin; D012110:Reserpine; D008238:Lysergic Acid Diethylamide; D003042:Cocaine; D010646:Phentolamine