Angiotensin 11 acting centrally contributes to the regulation of blood pressure and water intake and stimulates the release of catecholamines from the adrenal medulla. We hypothesized that the central angiotensin It is one mediator of biosynthesis of catecholamines in the adrenal medulla. Rats were administered icv angiotensin 11 or saline, and TH mRNA and protein levels in adrenal medulla were measured I or 3 It later. Angiotensin 11 did not change TH mRNA or protein I h later. However, by 3 It, angiotensin 11 increased TH mRNA and protein levels. Centrally administered angiotensin 11 elevates TH mRNA expression and protein levels in the adrenal medulla. In conclusion, one component of central angiotensin 11 elevation of blood pressure may be the result of increased catecholamine synthesis in the adrenal gland and elevated TH synthesis represents one underlying mechanism. (C) 2003 Elsevier Inc. All rights reserved.