title: The vasomotor effects of 5-hydroxytryptamine on equine basilar arteries in vitro.
abstract: The vasomotor effects of 5-hydroxytryptamine (5-HT) on isolated equine basilar arteries were studied. 5-HT induced contractions of equine basilar arteries in a concentration-dependent manner, with a pEC50 value (with 95% confidence limits) of 7.35 (7.08-7.62). Similar results were obtained with endothelium-denuded basilar arteries. Contractions were not competitively inhibited by the 5-HT2 receptor antagonist ketanserin at low concentrations of 5-HT. Conversely, at high concentrations of 5-HT, contractions were inhibited by ketanserin in a concentration-dependent manner, with a pA2 value of 8.91 (8.62-9.20). The 5-HT1 and 5-HT2 receptor antagonist methiothepin shifted the concentration-response curve of 5-HT downwards and to the right in a concentration-dependent manner. In the presence of 10(-6) mol/L ketanserin, however, methiothepin antagonized 5-HT-induced contractions competitively with a pA2 value of 7.95 (7.59-8.31). The 5-HT3 receptor antagonist MDL 72222 had no effect on 5-HT-induced contractions. The findings of this study indicate that 5-HT1 and 5-HT2 receptors are located in equine basilar arterial smooth muscle cells, and that stimulation of these receptors results in contraction.
authors.affiliation: Department of Veterinary Pharmacology, Faculty of Agriculture, Kagoshima University, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Miyamoto
authors.forename: T
authors.initials: T
authors.lastname: Obi
authors.forename: A
authors.initials: A
authors.lastname: Nishio
mesh_terms: D000818:Animals; D001488:Basilar Artery / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006736:Horses; D007650:Ketanserin / Q000494:pharmacology; D008719:Methiothepin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
chemical_list: D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D008719:Methiothepin; D007650:Ketanserin