ANGIOTENSIN RECEPTORS IN THE BRAIN

Angiotensin receptors have recently become a focus of scientific inter est due to the recent development of specific receptor ligands which a llow to distinguish between various angiotensin II receptor subtypes, notably the angiotensin II type 1 receptor (AT(1)) and angiotensin II type 2 receptor (AT(2)). Although both receptors belong to the seven t ransmembrane domain receptor family they feature less than 35% homolog y and differ in their signal transduction mechanisms and in the effect s mediated. In the brain, both angiotensin receptor types and probably some further subtypes are present and have been localized in distinct regions. In the adult brain, the AT(1) receptor dominates by far and is responsible for most of the known central actions of angiotensin pe ptides, for example blood pressure increase, release of vasopressin fr om the pituitary gland, natriuresis, drinking and induction of immedia te early genes in distinct brain areas. Some of the AT(1) receptor-med iated effects have been shown to be enhanced by blockade of AT(2) rece ptors in the brain suggesting that the central AT(2) receptor can exer t an inhibitory control on AT(1) receptor-mediated actions in the brai n.