Review: The renin-angiotensin system in the brain: an update

Angiotensin II (Ang II), the effector peptide of the renin-angiotensin system (RAS), plays a key role in the regulation of cardiovascular and body fluid and electrolyte homeostasis. The major actions of Ang II are mediated by two subtypes of G-protein-coupled angiotensin receptors, the AT 1-and the AT 2-receptor. Both receptors are seven transmem-brane glycoproteins with only 32–34% sequence similarity. Most of the classical actions of Ang II on fluid and blood pressure (BP) homeostasis are mediated by AT 1-receptors. However, this receptor subtype may also initiate proliferation, hypertro-phy and growth in various tissues. The AT 2-receptor is expressed with high density during foetal development and is less abundant in adult tissues, including the brain.