ANGIOTENSIN-II INDUCES REDUCED OXYTOCIN BUT NORMAL CORTICOTROPIN RELEASE IN RATS WITH LESIONS OF THE SUBFORNICAL ORGAN

The subfornical organ (SFO) was suggested to be the site of the central nervous system which mediates the stimulatory effect of angiotensin II (AII) on corticotropin (ACTH) release. To verify this hypothesis, ACTH response to peripherally administered AII was measured in rats with electrolytic lesion of the SFO. Increase in ACTH levels in response to AII (0.5 mu g/kg or 2.0 mu g/kg iv within 2 min) in conscious cannulated rats was dose-related and it was not affected by SFO lesion. The short infusion of AII (2.0 mu g/kg) was enough to induce an elevation in plasma oxytocin. Oxytocin response to AII was reduced while that of aldosterone and blood pressure was not modified by SFO lesion. Our data show that an intact SFO is needed for a full response of oxytocin but not of ACTH release to peripherally injected AII.