Enalapril and autonomic reflexes and exercise performance.

Enalapril (10 mg), in young sodium replete normotensive males significantly reduced systolic and diastolic blood pressures in both the supine and erect posture without orthostatic effects. As with captopril (25 mg) erect and supine heart rate did not differ from that after inactive placebo even at the time of maximum blood pressure reduction. The absence of reflex bradycardia was not related to a sympatho-inhibitory effect as the responses to Valsalva's manoeuvre, cold stress and dynamic and isometric exercise were unchanged by enalapril. Plasma noradrenaline was not different from that found after placebo treatment. Increased parasympathetic tone may contribute to the absence of tachycardia after converting enzyme inhibitors.