Baroreceptor reflex in elderly essential hypertensives: effect of chronic inhibition of angiotensin converting enzyme.

Baroreflex function and plasma angiotensin II (Ang II) were examined in five elderly and five young or middle-aged essential hypertensive patients before and after enalapril treatment. Baroreflex sensitivity (BS) during blood pressure (BP) elevation by phenylephrine (PE) but not during BP reduction by sodium nitroprusside (SNP) was significantly attenuated in the elderly compared with the younger group, while plasma Ang II concentration was not different between the two groups. Enalapril treatment reduced BP without significant changes in heart rate and plasma norepinephrine in both groups, suggesting a leftward shift of barofunction curve. It also increased the BS in some cases in each group. However, plasma Ang II was not significantly reduced during enalapril treatment. The changes in BS did not correlate with changes in plasma Ang II. These results suggest that BS may be attenuated with increasing age independent of plasma Ang II and that ACE inhibitor influences the set point of the barofunction curv...