1. The effects of carotid baroreceptor stimulation (neck chamber) on systemic haemodynamics were determined for normotensive and borderline hypertensive subjects during periods of resting and isometric exercise.
2. Both groups reacted to baroreceptor stimulation with a similar decrease in mean arterial pressure and cardiac index at rest and during isometric exercise, but baseline heart rate decreased more in borderline hypertensive patients.
3. Baroreceptor stimulation elicited the same haemodynamic response at rest and during exercise-induced arterial pressure increase. Since the magnitude of arterial pressure had no bearing on the subsequent response, these data suggest resetting of baroreceptors during this short-term blood pressure increase.