V1B, a G protein coupled receptor, also called arginine vasopressin 1B (AVPR1B), is a receptor for neurohypophyseal peptide [Arg8]-vasopressin. V1B receptor was previously known as vasopressin 3 receptor or antidiuretic hormone receptor 1b. V1B has been shown to be expressed highly in the anterior pituitary gland, where it stimulates corticotrophin release, and also in low levels in the brain and adrenal glands. V1b receptor signals through phosphatidylinositol hydrolysis to mobilize intracellular Ca2+. A single nucleotide polymorphism in VIB receptor has been associated with susceptibility to depression in humans. Highly selective peptide and nonpeptide vasopressin receptor antagonists have been developed and pharmacological studies have provided evidence for its role in stress related behavior and disorders including anxiety disorders and depression, while deletion of the V1B gene in mice has been shown to greatly reduce aggression. In addition, knockout of V1B gene has shown reduction of vasopressin-stimulated insulin release from islet cells is mediated via V1b receptors.