vasopressin receptor subtype 1A, member of the class A family of seven-transmembrane G protein-coupled receptors
V1a-type receptor is a G(q/11)-coupled receptor that mediates blood vessel constriction. Vasopressin (also known as arginine vasopressin or anti-diuretic hormone) is synthesized in the hypothalamus and is released from the posterior pituitary gland. The actions of vasopressin are mediated by the interaction of this hormone with three receptor subtypes: V1aR, V1bR, and V2R. These subtypes are differ in localization, function, and signaling pathways. Activation of V1aR and V1bR stimulate phospholipase C, while activation of V2R stimulates adenylate cyclase. Although vasopressin and oxytocin differ only by two amino acids and stimulate the same cAMP/PKA pathway, they have divergent physiological functions. Vasopressin is involved in regulating blood pressure and the balance of water and sodium ions, whereas oxytocin plays an important role in the uterus during childbirth and in lactation.