The activity of Arginine Vasopressin receptor 1A (AVPR1A) is mediated by G proteins which stimulate a phosphatidylinositol-calcium second messenger system. Arginine Vasopressin 1A receptor belongs to the same subfamily of G-protein coupled receptors of AVPR1B, V2R and Oxytocin receptors. The receptor mediates cell contraction and proliferation, platelet aggregation, release of coagulation factor and glycogenolysis. V1A is coupled to Gq/11 proteins and is found at high density on smooth muscle cells. It is involved in regulation of blood pressure through arterial vasoconstriction and has been found to stimulate VEGF secretion. AVPR1A is widely expressed in the brain and it has been implicated in social behaviours, including affiliation and attachment and related to diseases as autism.