Central effects of angiotensin II in water and saline loaded rats

In unanesthetized water-loaded rats, intracerebroventricular (IVT) angiotensin II (AII) injections produce centrally mediated pressor effects and antidiuresis. Experiments were performed to evaluate the role of antidiuretic hormone (ADH) release versus neurogenic mechanisms in the antidiuretic responses to central AII median eminence lesions used to block ADH release abolish antidiuretic effects but only attenuated pressor responses to IVT AII infusions. Pretreatment with an intravenous infusion of ADH antibody had a similar effect. Central administration of AII in water and saline-loaded rats produced no change in effective renal plasma flow or glomerular filtration rate, Natriuretic and kaliuretic responses to IVT AII injections were similar to those observed to intravenous ADH infusions. These data are consistent with the suggestion that antidiuresis and osmotic excretion observed after IVT AII injections in the rats are the result of ADH release, and that neurogenic mechanisms play a major role in the blood pressure but not in the antidiuretic responses.