Central actions and brain receptor binding of angiotensin II: Influence of sodium intake

The effects of dietary sodium on the central actions of angiotensin II (AII) and on 125I-AII binding to brain membranes were investigated in rats fed a low-sodium or control diet and implanted with a permanent cannula into the lateral cerebral ventricle. Blood pressure (BP) responses to AII injections intracerebroventricularly (i.v.t.) were blunted in sodium-deficient rats compared with controls. The BP increases in response to i.v.t.-injected Carbachol were the same in the two groups. In sodium-depleted rats, water intake was lower than in controls after AII given i.v.t.; higher after 1.5% NaCl i.v.t.; and unchanged after Carbachol i.v.t. The pressor response to AII given i.v.t. was higher in spontaneously hypertensive rats (SHR) than Wistar-Kyoto (WKY) control rats. This hyperresponsiveness to central AII was abolished by feeding a low-sodium diet. Specific 125I-AII binding in vitro to brain membranes was consistently lower in sodium-depleted rats. The results suggest that sodium depletion modifies the central actions of AII. This may be related in part to changes in the binding properties of AII receptors in the brain.