Converting enzyme inhibitors cause pressure-independent resetting
of baroreflex control of sympathetic outflow.
Heesch, Cheryl M., M. Elizabeth Crandall, and John A. Turbek.
Department of Physiology, The Ohio State University, Columbus, OH
43210-1218
APStracts 2:0294R, 1995.
The current study was performed to determine whether baroreflex
resetting following acute administration of converting enzyme
inhibitors (CEI's) was dependent on the concomitant decrease in mean
arterial pressure (MAP). Reflex changes in lumbar sympathetic nerve
activity (LSNA) due to increases and decreases in mean arterial
pressure MAP [i.v. phenylephrine (PE) and nitroprusside infusions]
were determined in normotensive and renal hypertensive (1-kidney, 1
-clip) anesthetized WKY rats: 1.) before (control, C), 2.) 15 minutes
after i.v. captopril (CAP, 2 mg/kg) or enalaprilat (EN, 300 _g) and
3.) 15 minutes after MAP was returned to pre-CEI levels with i.v. PE.
CEI's decreased MAP and caused a leftward shift of the MAP-LSNA curve
towards a lower operating pressure range in all hypertensive and in
one group of normotensive rats. The baroreflex curve remained shifted
to the left even after MAP was restored to pre-CEI levels by infusion
of PE. Thus, CEI's cause a pressure-independent resetting of
baroreflex control of sympathetic outflow within 15 minutes. This
effect of CEI's is most likely due to elimination of a central
nervous system effect of circulating angiotensin II and could
contribute to the antihypertensive actions of this class of
compounds.
Received 31 March 1993; accepted in final form 18 October 1995.
APS Manuscript Number R174-3.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 November 95