Baroreceptor-induced decrease in muscle blood flow upon propranolol administration

The acute effects of propranolol, 1 mg/kg i.v., were studied in chloralosed, vagotomized cats. The vascularly isolated but innervated calf muscles were perfused from another animal. In one group of experiments, the carotid baroreceptors were exposed to ambient arterial pressure. Here, propranolol caused a fall in heart rate and an increase in resistance of the isolated muscle bed. In other experiments, the carotid sinuses were perfused at a constant pressure. In these animals, no increase in muscle flow resistance was observed after the drug. It is concluded that the increase in total peripheral resistance, seen initially upon propranolol administration, may be reflexly induced via the baroreceptors.