Localization of receptors for the dipsogenic action of angiotensin II in the subfornical organ of rat.

The proposal of the subfornical organ (SFO) as a site of receptors for drinking induced by angiotensin II (AII) was investigated with several mutually confirmatory experiments. Intracranial injections of physiological doses of AII elicited drinking if and only if applied directly to the SFO (Experiment I). Ablation of the SFO selectively (Experiment 2) and permanently (Experiment 4) eliminated drinking elicited by physiological doses of intravenously infused AII. Animals in which SFO had been ablated responded normally to cellular dehydration but reduced responding to the extracellular thirsts of beta-adrenergic activation and hyperoncotic colloid dialysis (Experiment 3). Infusion of saralasin, an AII antagonist, directly into the SFO selectively and reversibly antagonized intravenous AII drinking (Experiment 5). The hypothesis that the SFO contains dipsogenic receptors for circulating AII is strongly supported.