Demonstration of alpha-adrenoceptor antagonism by the 5HT2 antagonist, ketanserin (R49945), in sheep.
Serotonin causes a dose related (0.1-20 micrograms/kg i.v.) increase in mean arterial blood pressure (MAP) and heart rate in conscious sheep. Ketanserin (0.1 mg/kg per h i.v.) causes a decrease in blood pressure, and an increase in heart rate. In the presence of ketanserin, serotonin induced increases in MAP are attenuated, or abolished, but the increases in heart rate are enhanced. Ketanserin (10 mg/kg per h i.v.) attenuates or abolishes the increase in blood pressure induced by the alpha-adrenoceptor agonist phenylephrine in conscious sheep. When administered in the presence of the alpha-adrenoceptor antagonist prazosin, ketanserin (0.1 mg/kg per h i.v.) fails to induce a further hypotensive response. These data suggest that in the conscious sheep ketanserin exhibits predominantly alpha-adrenoceptor antagonism.
D000317:Adrenergic alpha-Antagonists; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D007650:Ketanserin; D010880:Piperidines / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology*; D012756:Sheep
D000317:Adrenergic alpha-Antagonists; D010880:Piperidines; D012702:Serotonin Antagonists; D012701:Serotonin; D007650:Ketanserin