Serotonin-induced vasoconstriction in rabbit femoral artery: mediation by both 5-HT2 serotonergic and alpha 1-adrenoceptors.
We determined the receptors mediating the contractile response of the rabbit femoral artery to serotonin in isolated vascular rings mounted in tissue baths for the measurement of isometric contraction. Serotonin elicited a biphasic concentration-response curve (CRC). The threshold and maximal concentrations of the first phase were 0.03 and 3 microM, respectively. The respective values for the second phase were 10 and 1,000 microM. Benextramine, a selective, irreversible alpha-adrenoceptor antagonist, eliminated the second phase. Similar results were obtained with benextramine in femoral arteries acutely denervated with 6-hydroxydopamine (6-OHDA). In contrast, the reversible, competitive 5-HT2 antagonist ketanserin shifted the first phase of the serotonin CRC to the right ina concentration-dependent manner but had little or no effect on the second phase. No evidence for functional alpha 2-adrenoceptors was found. We conclude that the first phase of the serotonin CRC in rabbit femoral artery was mediated predominantly by 5-HT2 receptors and that the second phase was mediated by alpha 1-adrenoceptors.
Grandaw
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Department of Pharmacology, College of Medicine, University of California, Irvine 92717, USA.
Purdy
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RE
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D003000:Clonidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005263:Femoral Artery / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D007537:Isometric Contraction; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D011817:Rabbits; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects*; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D012701:Serotonin; D003000:Clonidine; D008784:Methysergide