AVPR1B (vasopressin V1b receptor, V1BR) is a receptor for arginine vasopressin. It belongs to the subfamily of G-protein coupled receptors which includes AVPR1A, V2R and OXT receptors. AVPR1B has important functions in behavioral modulation, social recognition memory, social aggression, and regulation of hormonal stress. It is relevant to neuropsychiatric disorders including major depression, and specific haplotypes of AVPR1B seem to have protective effects against depressive disorders. In cancer, AVPR1B is expressed at high levels in ACTH-secreting pituitary adenomas, and it also has positivity in bronchial carcinoids (responsible for ectopic ACTH syndrome). In immunohistochemistry, AVPR1B has membranous positivity. The receptor is primarily located in anterior pituitary corticotrophs, where it stimulates ACTH release. However, it is also found in other regions in the brain, such as in hippocampal CA2 pyramidal cells, and may show limited extrapituitary positivity in the breast, lung, heart, kidney, thymus, spleen and uterus. References: Crit Care. 7 (6): 427–34, PMID: 14624682; Neuroscience. 143 (4): 1031–9, PMID: 17027167; Proc Natl Acad Sci U S A. 1995 Jul 18;92(15):6783-7, PMID: 7624319; Mol. Psychiatry. 9 (3): 287–92,. PMID: 15094789; J. Clin. Invest. 97 (5): 1311–8, PMID: 8636444; Front Neurosci. 2017 Oct 16;11:567