Participation of hypothalamic paraventricular nucleus in locus
coeruleus-induced baroreflex suppression in the rat.
Shih, Cheng-Dean, Samuel H. H. Chan, and Julie Y. H. Chan.
Institutes of Physiology and Pharmacology, National Yang-Ming
University, Taipei 11221, Taiwan, and Department of Medical Research,
Veterans General Hospital-Taipei, Taipei 11217, Taiwan, Republic of
China
APStracts 2:0058H, 1995.
We evaluated the potential role of the paraventricular nucleus of
hypotha lamus (PVN) in the suppression of baroreceptor reflex (BRR)
response by locus coeruleus (LC), using adult male Sprague-Dawley
rats anesthetized with pentobarbital sodium. Electrical stimulation
of histologically verified sites in the LC elicited significant
reduction in the BRR response. This suppressive effect of LC on BRR
response was appreciably antagonized by bilateral electrolytic
lesions of the PVN, and reversibly blocked by bilateral
microinjection of 2% lidocaine into similar hypothalamic loci. Local
admin istration of the [alpha]1-adrenoceptor antagonist, prazosin (50
pmol), or an antiserum directed against neuropeptide Y (NPY) (1:20),
into the bilateral PVN also significantly attenuated the suppression
elicited by LC on BRR response. In contrast, treatments with the
[alpha]2-adrenoceptor blocker, yohimbine (50 pmol), heat-inactivated
NPY antiserum (1:20), aCSF, or normal rabbit serum (1:20) produced no
discernible effect. These results suggest that the PVN may constitute
part of the efferent pathways through which LC elicits its inhibition
on the BRR response. Furthermore, LC may activate this pathway via
[alpha]1-adrenoceptors and NPY receptors in the PVN.
Received 24 October 1994; accepted in final form 15 February
1995.
APS Manuscript Number H943-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 7 March 1995.