Journal of Neuroscience, Vol 11, 1531-1539, Copyright © 1991 by Society for Neuroscience
Septal arginine vasopressin (AVP) receptor regulation in rats depleted of septal AVP following long-term castration
P Poulin and QJ Pittman
Department of Medical Physiology, University of Calgary, Alberta, Canada.
Arginine vasopressin (AVP) causes severe motor disturbances, including
barrel rotations and myotonic/myoclonic convulsions, following repeated
injections into either a lateral cerebral ventricle or the ventral septal
area (VSA) of the rat brain. Because the AVP content of the rat septal area
has been shown to be virtually eliminated following long- term castration,
and because removal of a receptor ligand typically results in receptor
upregulation and behavioral supersensitivity to the ligand, we tested the
hypothesis that long-term castrated rats may be supersensitive to the motor
actions caused by centrally injected AVP and may have upregulated septal
AVP receptors. In these experiments, adult male Wistar rats were used 5
months after castration or, as controls, after sham castration. The
effectiveness of long-term castration in eliminating AVP content of the VSA
was indicated by the observation that a priming hypertonic saline stimulus
(known to induce the central release of AVP and sensitize the rat brain)
sensitized the brains of sham control rats but not of the castrated rats to
the motor actions of a subsequent intracerbroventricular injection of AVP.
The motor actions of centrally injected AVP, as well as septal AVP receptor
characteristics (number and affinity), and AVP-stimulated phosphoinositide
(PI) hydrolysis were then investigated in long-term castrated and sham
control rats. Motor disturbances induced by either a first or a second
injection of AVP were not greater in long-term castrated rats than in sham
controls.(ABSTRACT TRUNCATED AT 250 WORDS)