AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 1 51-R57, Copyright © 1983 by American Physiological Society
Preoptic-hypothalamic periventricular lesions reduce natriuresis to volume expansion
S. L. Bealer, J. R. Haywood, K. A. Gruber, V. M. Buckalew Jr, G. D. Fink, M. J. Brody and A. K. Johnson
The present experiment was designed to determine if electrolytic ablation
of the periventricular tissue surrounding the anteroventral third ventricle
(AV3V) altered the natriuresis typically seen during isotonic volume
expansion. Control and AV3V-lesioned rats received intravenous infusions of
0.9% NaCl at 0.5 ml/min until 10% body weight was given. Arterial blood
pressure was monitored, and urine was collected throughout the experiment.
Following expansion, blood was processed for analysis of natriuretic
hormonelike activity by chromatographic separation of plasma extracts
followed by measuring antinatriferic activity across the isolated toad
bladder. Urinary sodium excretion and urine volume during expansion were
significantly less in rats with lesions surrounding the AV3V region than in
control rats. Toad bladder bioassay showed a high level of natriuretic
hormonelike activity in control animals following volume expansion, but no
natriuretic hormonelike activity in plasma from volume-expanded rats with
AV3V lesions. These data demonstrate that AV3V periventricular ablation
attenuates the natriuresis induced by isotonic-volume expansion. In
addition, preliminary results indicate the AV3V region may be a central
site critical for natriuretic hormonelike activity and control of
extracellular fluid volume.
