Rapid elicitation of salt appetite by an intravenous infusion of
angiotensin ii in rats.
Fitts, Douglas A., and Robert L. Thunhorst.
Department of Psychology, University of Washington, Seattle, WA
98195-1525 and Department of Psychology, University of Iowa, Iowa
City, IA, 52242-1407
APStracts 2:0334R, 1995.
A role for the renal renin-angiotensin system in the direct
stimulation of salt appetite in the rat remains controversial because
attempts to elicit the behavior by intravenous (iv) administration of
angiotensin II (ANG II) have been unconvincing. We recently
demonstrated that depletion-induced salt appetite was attenuated by
selective blockade of peripheral ANG II synthesis with an iv dose of
converting-enzyme inhibitor (captopril, CAP) that does not block the
synthesis of ANG II inside the blood-brain barrier. We now show that
iv ANG II at 30 ng/min rapidly re-establishes salt appetite in CAP
-blocked rats. The mean arterial blood pressure (MAP) of unblocked
sodium-depleted rats was normal, but CAP- blocked depleted rats had
low MAP. An iv infusion of ANG II in CAP-blocked rats brought MAP
into the normal range and elicited water and salt drinking within 90
min. Phenylephrine also normalized MAP but failed to elicit fluid
intake in CAP-blocked sodium-deficient rats. Sodium and water
balances tended to be more positive during ANG II than during
phenylephrine infusions. Thus, circulating ANG II may stimulate both
thirst and salt appetite by a direct action on the brain and not by
causing natriuresis or by raising the blood pressure.
Received 7 August 1995; accepted in final form 27 November 1995.
APS Manuscript Number R495-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95