Preoptic recess alpha-adrenoceptors control cardiovascular
responses to hyperosmolality.
Bealer, Steven L.
Department of Physiology and Biophysics, University of Tennessee,
Memphis, Memphis, TN 38163
APStracts 3:0429R, 1996.
The roles of alpha-adrenoceptors in the anteroventral third ventricle
(AV3V) and diagonal band of Broca (DBB) in cardiovascular responses
to peripheral hypertonicity were investigated in conscious rats.
Normal artificial cerebrospinal fluid (ACSF), or ACSF containing
phentolamine (alpha-1 and alpha-2 antagonist), yohimbine (alpha-2
antagonist) or prazosin (alpha-1 antagonist) was perfused through
microdialysis probes in the DBB, AV3V, or lateral ventricle during a
30 min iv infusion of isotonic (0.17 M; 0.1 or 1.7 ml/kg/min) or
hypertonic (2.5 M; 0.1 ml/kg/min) NaCl. Hypertonic infusion increased
blood pressure (MAP; 172 mmHg) and decreased heart rate (HR; 366
bpm). Both responses were abolished by AV3V administration of
phentolamine or yohimbine, while prazosin selectively prevented the
bradycardia. Phentolamine in the DBB or lateral ventricle did not
alter either response. Stimulation of AV3V alpha-1 adrenoceptors
(phenylephrine) decreased HR and MAP, while alpha-2 adrenoceptor
stimulation (clonidine) produced bradycardia, but increased MAP. Data
suggest that alpha-adrenoceptors in the AV3V, but not DBB, regulate
cardiovascular responses to hyperosmolality.
Received 13 June 1996; accepted in final form 19 November 1996.
APS Manuscript Number R341-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996