Hypothalamic sites mediating cardiovascular effects of
microinjected bicuculline and excitatory amino acids in rats.
Novellis, Vito De, Elizabeth Stotz-Potter, S. Michelle Morin,
Francesco Rossi, and Joseph A. Dimicco1.
Department of Pharmacology and Toxicology, Indiana University
School of Medicine, Indianapolis, Indiana 46202, and Institute of
Pharmacology and Toxicology, First Faculty of Medicine and Surgery,
University of Naples, Naples Italy
APStracts 2:0036R, 1995.
Microinjection of the GABAA receptor antagonist bicuculline methiodide
(BMI) into either the dorsomedial hypothalamic nucleus (DMH) or the
nearby paraventricular hypothalamic nucleus (PVN) has been reported
to evoke marked tachycardia and modest pressor effects. We compared
the effects of microinjecting BMI and excitatory amino acids into (1)
the DMH, (2) the PVN, and (3) an intermediate area between the two
nuclei. In conscious rats, microinjection of BMI 10 pmol, kainic acid
0.5 pmol, or NMDA 5 pmol into the DMH markedly increased heart rate
and slightly elevated arterial pressure, while injections into other
regions provoked changes that progressively declined in magnitude
with increasing distance from the nucleus. A similar pattern was
evident in urethane anesthetized rats, where the shortest latency to
onset of BMI-induced increases in heart rate was seen after injection
into the DMH. These findings demonstrate that the cardiovascular
changes seen after microinjection of BMI or excitatory amino acids
into the medial hypothalamus result from an action in the DMH and not
from spread to the PVN.
Received 29 August 1994; accepted in final form 1 February 1995.
APS Manuscript Number R482-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.