Captopril and baroreceptor reflex responses to pressor and depressor stimuli in the rabbit.

1. The reflex effects of intravenous phenylephrine, sodium nitroprusside or acute haemorrhage in rabbits were examined as indices of baroreceptors reflex function. 2. The slope of the linear regression of heart period: mean arterial pressure relationship was significantly greater (P less than 0.01) when buffering the pressor stimulus than either depressor stress. 3. Captopril (1 mg/kg i.v.) had no effect on the slope of the relationship to either pressor or depressor stimuli. 4. The clinical and experimental observation of hypotension without bradycardia after captopril could not be confirmed in the present study to be a result of changes in baroreflex sensitivity.