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Hypertension, Vol 15, 284-290, Copyright © 1990 by American Heart Association

ARTICLES

Baroreceptor reflex enhancement by chronic intracerebroventricular infusion of enalapril in normotensive rats

RD Bunag, L Eriksson and S Tanabe
Department of Pharmacology, College of Health Sciences and Hospital, University of Kansas Medical Center, Kansas City 66103.

Involvement of the brain renin-angiotensin system in baroreceptor reflex regulation was assessed by recording reflex heart rate and sympathetic nerve responses in normotensive rats that had been infused intracerebroventricularly with the converting enzyme inhibitor enalapril for 15 days. Reflex bradycardia and sympathetic nerve inhibition during pressor responses to phenylephrine were larger in rats with intracerebroventricularly infused enalapril than in control rats similarly infused either intracerebroventricularly with saline or intravenously with enalapril. In contrast, opposite reflex responses to sodium nitroprusside-induced hypotension were mostly unaffected. Because depressor, bradycardic, and sympathoinhibitory responses to electrical stimulation of the central cut end of the left aortic depressor nerve were also enhanced, intracerebroventricularly infused enalapril must be affecting the baroreceptor reflex arc centrally. These results are compatible with the interpretation that intracerebroventricularly infused enalapril enhanced baroreceptor reflex sensitivity by reducing endogenous angiotensin II levels in the brain through converting enzyme inhibition.