Central H1 and H2 receptor participation in the control of water and salt intake in rats.

The aim of the present study was to evaluate the participation of brain H1 and H2 histaminergic receptors on water and salt intake induced by water deprivation (24 h), furosemide-induced sodium depletion and central angiotensinergic pharmacological stimulation in rats. Third ventricle injections of the H1 and H2 receptor antagonists, mepyramine (50, 100, 200 and 400 nmol) and cimetidine (100, 200 and 400 nmol), were unable to modify water intake induced by water deprivation and sodium depletion. Salt intake elicited by water deprivation and sodium depletion was reduced by the central administration of mepyramine, while intracerebroventricular administration of cimetidine had no effect. Water and salt intake evoked by central angiotensinergic stimulation (10 ng) was diminished by third ventricle injections of both mepyramine and cimetidine. Inhibition of the ingestive behaviors observed here is not a result of any illness-like effect produced by the intracerebroventricular injections of the histaminergic antagonists used, as demonstrated by an avoidance test. It was also shown that third ventricle injections of these compounds were unable to modify the hedonic behavior that leads rats to drink a tasty saccharin solution. We conclude that central histaminergic receptors participate in the control of salt intake induced by distinct physiological and pharmacological stimuli.