AJP - Endocrinology and Metabolism, Vol 259, Issue 3 E432-E436, Copyright © 1990 by American Physiological Society
Effects of naloxone on renin and pressor responses to acute renal hypotension in rats
C. J. Weaver and M. D. Johnson
Department of Physiology, West Virginia University, Morgantown 26506.
Reduction of renal perfusion is followed by increases in plasma renin
activity (PRA) and arterial pressure. The present experiments were designed
to determine if an opiate antagonist would alter pressor or renin responses
to acute reduction of renal arterial pressure (RAP) in anesthetized rats.
Male Sprague-Dawley rats were anesthetized with Inactin, and an adjustable
constrictor device was placed around the abdominal aorta proximal to the
renal arteries. One-half of the animals were pretreated with the opiate
antagonist naloxone (2 mg/kg iv), and the other one-half were pretreated
with saline vehicle. The abdominal aorta was then constricted to reduce RAP
by 25% (measured as femoral arterial pressure) in one-half of the animals
in each pretreatment group. Compared with vehicle pretreatment, naloxone
pretreatment did not alter the PRA response to aortic constriction;
however, naloxone did attenuate the pressor response. We conclude that 1)
the PRA response to acute reduction of renal arterial pressure is not
dependent on an opiate mechanism in the rat, and 2) attenuation of the
pressor response to aortic constriction by naloxone in intact rats is not
secondary to a suppression of the PRA response.
