Captopril inhibits pressor responses to peripheral sympathetic nerve activation in cats and rats.

1. In cats, under chloralose anaesthesia, captopril (0.1-0.3 mg/kg i.v.) inhibited the potentiation of the pressor effects of the ganglion stimulant McNeil-A-343 caused by intravenous infusion of angiotensin I (0.1 microgram/min). 2. In both cats and rats under chloralose anaesthesia captopril (0.01-1.0 mg/kg i.v.) depressed pressor responses to McNeil-A-343 whilst not modifying those to bilateral occlusion of the carotid arteries, or intravenous injection of the ganglion stimulant dimethylphenylpiperazinium or adrenaline. 3. It is concluded that in the cat and rat captopril depresses cardiovascular responses to sympathetic postganglionic nerve activation, both in the presence and absence of exogenous angiotensin I by an action which is proximal to the terminal synapse.