AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 6 1170-R1176, Copyright © 1986 by American Physiological Society
Possible mechanism for increased beta-adrenergic dipsogenic response in food-deprived rats
L. F. Yeh, S. P. Baker and M. J. Katovich
The dipsogenic responsiveness to isoproterenol was studied in food-deprived
male rats. Unstimulated water intake was similar between control and fasted
groups, and parallel dose-response curves for the dipsogenic response
induced by isoproterenol (10-50 micrograms/kg) were observed. A twofold
elevation in dipsogenic responsiveness was observed in the fasted rats, and
this enhanced response was correlated with a dose-dependent increase in
plasma renin activity when compared with the control rats after
administration of isoproterenol. beta-Adrenergic receptor binding assays
were performed on both heart and renal cortical tissues. In the heart the
receptor concentration was decreased after food deprivation, whereas the
affinity of the receptor for the beta-adrenergic antagonist [125I]CYP
remained unchanged. On the other hand, an increased beta-adrenergic
receptor concentration without change in affinity was found in renal
cortices of fasted rats. Results from these receptor binding studies
correlated with the attenuated chronotrophic response and the increased
dipsogenic response to beta-adrenergic stimulation in the fasted rat.
Therefore stimulation of these increased renal receptors by isoproterenol
could result in an enhanced activation of the renin-angiotensin system and
thus be a factor responsible for the increased dipsogenic response induced
by isoproterenol observed in the fasted rats.
