V1 receptors activate phospholipases A2, C, and D, resulting in the production of inositol 1,4,5-trisphosphate (IPS) and 1,Z-diacylglycerol (DAG), the mobilization of intracellular Ca2+, the influx of extracellular Ca2+, the activation of protein kinase C, and protein phosphorylation4. V1A AVP receptors have been shown by radioligand binding techniques to be present in vascular smooth muscle cells, hepatocytes, blood platelets, lymphocytes and monocytes, type 2 pneumocytes, adrenal cortex, brain (hippocampus septum et amygdalae), reproductive organs, retinal epithelium, renal mesangial cells, and the A10, A7r5,3T3, and WRK-1 cell lines4. V1A AVP receptors mediate cell contraction and proliferation, platelet aggregation, coagulation factor release, and glycogenolysis. V1B AVP receptors are located in the anterior pituitary where they stimulate ACTH release