Possible dual effect of endogenous ANP on water and sodium intake and role of AII.

Water intake may or may not be associated with sodium appetite. There are excitatory and inhibitory mechanisms that control these behaviors whose mediators and interactions are unclear. We investigated the effects of specific antisera against angiotensin II (AB-AII) and atrial natriuretic peptide (AB-ANP) on the induction of the two behaviors in rats deprived of water overnight or normally hydrated and submitted to intracerebroventricular (icv) microinjection of AII. AB-ANP reduced water intake induced by overnight deprivation but not by icv microinjection of AII, while AB-AII reduced water intake in both situations. AB-ANP and AB-AII increased saline intake in deprived animals and decreased saline intake induced by icv microinjection of AII in normally hydrated animals. The effect of AII on water and sodium intake may depend, at least in part, on an interaction with the system of ANP neurons. This peptide, in turn, may have different actions on water and sodium intake as a function of extracellular fluid conditions and of AII levels.