[1] V1 receptors (V1Rs) are found in high density on vascular smooth muscle and cause vasoconstriction by an increase in intracellular calcium via the phosphatidyl–inositol-bisphosphate cascade.
Additionally V1R are located in brain, testis, superior cervical ganglion, liver, blood vessels, and renal medulla.
However, V3R has a pharmacologic profile that distinguishes it from the human V1R and activates several signaling pathways via different G-proteins, depending on the level of receptor expression.
In the kidney, AVPR2's primary function is to respond to arginine vasopressin by stimulating mechanisms that concentrate the urine and maintain water homeostasis in the organism.
Most commonly VRAs are used to treat hyponatremia caused by syndrome of inappropriate antidiuretic hormone secretion (SIADH), congestive heart failure (CHF) and cirrhosis.
[5] Normally, when osmolality falls below its set point, plasma vasopressin levels become undetectable, and an aquaresis results.
[2] Vasopressin receptor antagonists include the new class of "vaptan drugs" such as conivaptan, tolvaptan, mozavaptan, lixivaptan, satavaptan etc.