Effect of autonomic blocking agents on the cardiovascular effects of octapressin in the rat

Abstract

Cardiovascular effects of Octapressin were studied in anesthetized male albino rats. The effect of pretreatment with the following blocking agents was evaluated: atropine, phenoxybenzamine, propranolol, hexamethonium and chlorpromazine. A decrease in blood pressure and in heart rate was induced by phenoxybenzamine; propranolol treatment caused a decrease in heart rate and an increase in circulation time. Injections of 2, 6 and 18 mU Octapressin caused no changes in cardiac output or in central venous pressure. The increase in blood pressure following Octapressin was found to be dose-dependent in the saline-treated controls as well as in the rats pretreated with the autonomic blocking agents. The pressor response to Octapressin was increased by atropine, phenoxybenzamine, propranolol and chlorpromazine. From these data it is concluded that the increase in blood pressure following Octapressin is caused by an increase in vascular resistance in the systemic circulation