Matching to sample, blood pressure and hormonal effects of chronic enalapril in baboons

Sensory and behavioral performance of three normotensive and one renovascular hypertensive baboon was tested before, during and following chronic oral dosing with the angiotensin converting enzyme (ACE) inhibitor enalapril. Performance measurements during a five-color simultaneous matching to sample task were obtained during enalapril dosing of 0.18 and 0.61 mg/kg/day, and vehicle. Each dose was administered for 21 consecutive days preceded and followed by 14 baseline and recovery periods, respectively. BP from awake animals as well as serum ACE activity were measured. Systolic BPs decreased by a maximum of 6-8% (8 mmHg). ACE activity was decreased in a dose-dependent fashion by 54.01% and 81.63% for 0.18 mg/kg and 0.61 mg/kg doses, respectively. At 0.61 mg/kg, the duration of simple key-press motor behavior increased by 15% in the first week and then progressively returned to baseline levels. Systematic changes in choice reaction times or color discrimination accuracy were not observed. Although the renovascular hypertensive baboon displayed greater hypotension and ACE inhibition, behavioral effects were not significantly different from normotensive baboons. The present study extends to sensory functions the lack of adverse behavioral side-effects of enalapril.