Angiotensin-induced drinking and the effect of bilateral nephrectomy

The induction of drinking by the intraventricular administration of angiotensin II has been attributed to a specific interaction with receptors in the medial preoptic-anterior hypothalamic border. These studies have been pharmacological in nature, involving exogenous peptide. In experiments reported elsewhere the present authors have shown that nephrectomy resulted in a regionally selective increase in levels of brain angiotensinogen, the putative prohormone of any CNS angiotensin peptides. Nephrectomy also markedly perturbs fluid and ion homeostasis. A study was therefore made of the effect of bilateral nephrectomy on spontaneous and angiotensin-induced drinking behavior. A deficit in spontaneous drinking following nephrectomy was observed, but it was noted that this related directly to diminished food intake. Angiotensin II-induced drinking was markedly potentiated following nephrectomy, indicative of possible up-regulation of angiotensin receptors in selected regions of the rat brain. The results are consistent with a physiological role for angiotensin in regulating fluid intake and volume homeostasis.