Interaction between Dopaminergic and Angiotensinergic Systems on Thirst in Adult Male Rats

Abstract

Thirst, which provides the motivation to drink, is an important component of the coordinated sequence of physiological responses that maintain the volume and composition of body fluids. Special structures in the central nervous system like periventricular organs detect changes in these parameters continuously. The present study investigated the interaction between dopaminergic and angiotensinergic systems on water intake in adult male rats. Intracerebroventricular (ICV) injections were carried out in all experiments after 24 h deprivation of water intake. After the deprivation interval, the volume of consumed water was measured for 1 h. Administration the angiotensinergic (AT 1 ) receptor antagonist Losartan (45 µg/rat), and the dopaminergic antagonist Chlorpromazine (40 µg/rat) significantly decreased water intake when compared to saline-treated controls. In contrast, ICV microinjection of the dopaminergic agonist Bromocriptine (10 µg/rat) significantly increased water intake when compared to saline-treated controls. ICV injection of Bromocriptine 15 min after Losartan administration was able to attenuate the inhibitory effect of Losartan on water intake, whereas administration of Chlorpromazine 15 min after Losartan was unable to change the Losartan effect. These results suggest that the dopaminergic system interactions with the angiotensinergic system to regulate water intake through circumventricular organs. Dopaminergic and angiotensinergic neurons can monitor and regulate water intake via the stimulatory and inhibitory effects on each other, respectively.