Vasopressin receptors belong to the family of G protein–coupled receptors. V1 receptors are coupled to Gq and V2 receptors are coupled to Gs. When vasopressin binds to the V1 receptor, phospholipase C is activated with the eventual production of InsP3 and 1,2 DG. These molecules serve to increase the release of calcium from the endoplasmic reticulum as well as increase the entry of calcium through gated channels. The increase in intracellular calcium leads to an increase in the activity of myosin light chain kinase.
