Electrolytic lesions of periventricular tissue surrounding the anteroventral third ventricle (AV3V) results in chronic hypernatremia and attenuates natriuresis following several experimental treatments. The present investigation was designed to determine if AV3V periventricular ablation results in acute postlesion alterations in sodium metabolism. Urinary sodium excretion was measured during 2-h periods for 6 h, and then daily for 7 days following either electrolytic ablation of AV3V periventricular tissue or control surgery. Similar measurements were carried out on unoperated control animals, and rats which had received either renal denervations or subcutaneous injections of deoxycorticosterone (DOC) prior to surgery. Lesions of the tissue surrounding the AV3V resulted in a natriuresis and polyuria that was not prevented by renal denervation or DOC treatment and was accompanied by a pressor response and decreased glomerular filtration rate. The initial natriuresis was followed by 2 days of sodium retention, which exceeded the amount necessary to restore sodium balance. These data demonstrate that ablation of AV3V periventricular tissue results in acute alterations in sodium metabolism, and support the hypothesis that tissue surrounding the AV3V contains neural elements critical for normal sodium regulation.