Angiotensin Receptors in the Brain

Angiotensin receptors have recently become a focus of scientific interest due to the recent development of specific receptor ligands which allow 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 transmembrane domain receptor family they feature less than 35% homology and differ in their signal transduction mechanisms and in the effects 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 peptides, for example blood pressure increase, release of vasopressin from the pituitary gland, natriuresis, drinking and induction of immediate early genes in distinct brain areas. Some of the AT 2 receptor‐mediated effects have been shown to be enhanced by blockade of AT 2 receptors in the brain suggesting that the central AT 2 receptor can exert an inhibitory control on AT 1 receptor‐mediated actions in the brain.