AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 2 496-R502, Copyright © 1994 by American Physiological Society
Role of lateral hypothalamus on fluid, electrolyte, and cardiovascular responses to activation of the MSA
A. S. Haibara, W. A. Saad, J. V. Menani, L. A. Camargo and A. Renzi
Department of Physiology, School of Dentistry, Paulista State University, Araraquara, Sao Paulo, Brazil.
In this study we investigated the influence of electrolytic lesion or of
opioid agonist injections into the lateral hypothalamus (LH) on the
dipsogenic, natriuretic, kaliuretic, antidiuretic, pressor, and
bradycardiac effects of cholinergic stimulation of the medial septal area
(MSA) in rats. Sham- and LH-lesioned male Holtzman rats received a
stainless steel cannula implanted into the LH. Other groups of rats had
cannulas implanted simultaneously into the MSA and LH. Carbachol (2 nmol)
injection into the MSA induced water intake, pressor, and bradycardic
responses. LH lesion reduced all of these effects (1-3 and 15-18 days).
Previous injection of synthetic opiate agonist, FK-33824 (100 ng), into the
LH reduced the water intake, natriuresis, kaliuresis, and pressor responses
induced by carbachol injected into the MSA. These data show that both
electrolytic lesion or injection of an opiate agonist in the LH reduces the
fluid-electrolyte and cardiovascular responses to cholinergic activation of
the MSA. The involvement of LH with central excitatory and inhibitory
mechanisms related to fluid-electrolytic and cardiovascular control is
suggested.
