AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 1 45-R50, Copyright © 1983 by American Physiological Society
Effect of forebrain lesions on response to chronic intraventricular angiotensin II
G. D. Fink, W. J. Bryan and M. E. Mann
We previously reported that chronic (10 days) intracerebroventricular (ivt)
infusion of angiotensin II (ANG II) into conscious rabbits produced a
significant rise in mean arterial pressure (MAP), water intake (WI), and
urinary sodium excretion (UNaV), and a significant fall in plasma sodium
(PNa) and potassium (PK) concentrations. Urinary potassium excretion (UKV)
and body fluid volume were not changed significantly. In the present
experiments, similar chronic infusions were carried out in intact rabbits
and in rabbits with an electrolytic lesion placed in the anteroventral
third cerebral ventricle (AV3V) region. Integrity of the AV3V area is
essential for normal expression of a variety of acute physiological
responses to ANG II injected into the brain. In rabbits with AV3V lesions,
chronic ivt infusion of ANG II did not significantly alter MAP, but WI and
fractional UNaV increased, and PNa decreased in a manner identical to that
of sham-lesioned control rabbits. Plasma and extracellular fluid volumes
increased, and body weight and food intake decreased in all rabbits during
ANG II infusion, but to a slightly greater extent in the AV3V-lesioned
rabbits. We conclude that an intact AV3V region is crucial for the
hypertensive effect of chronic ivt fusions of ANG II in the rabbit but is
not necessary for most of the fluid and electrolyte alterations associated
with such infusions.
