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 centra l nervous system which mediates the stimulatory effect of angiotensin II (AII) on corticotropin (ACTH) release. To verify this hypothesis, A CTH response to peripherally administered AII was measured in rats wit h 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 cannu lated 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 o f aldosterone and blood pressure was not modified by SFO lesion. Our d ata show that an intact SFO is needed for a full response of oxytocin but not of ACTH release to peripherally injected AII.