The neurohypophysial hormone arginine vasopressin (AVP) is involved in diverse functions including regulation of body fluid homeostasis, vasoconstriction, and adrenocorticotropic hormone release. These physiological effects are mediated by three subtypes of vasopressin receptors, designated V1a, V1b (or V3), and V2. They all belong to the large rhodopsin-like G-protein-coupled receptor family.
The V1a receptor is expressed in both neuronal and non-neuronal tissues including the heart and elicits a variety of physiological effects including cell contraction and proliferation, stimulation of hepatic glycogenolysis, platelet aggregation and coagulation factor release. The V1b receptor subtype is found predominantly in the pituitary gland where it stimulates adrenocorticotropic hormone release. Both the V1a and V1b AVP receptors act through a G protein alpha-subunit of the Gαq family (αq, q11, q14, α15/16) to activate phospholipase C-β, and, thus enhance cellular IP3 and calcium levels. By contrast, the V2 receptor subtype is localized predominantly to the kidney where it mediates the anti-diuretic effects of AVP through the heterotrimeric G protein Gs and activation of adenylyl cyclase.
