Vasopressin

Vasopressin (antidiuretic hormone, ADH, arginine vasopressin/AVP) is a nonapeptide hormone produced in the hypothalamus and released from the posterior pituitary. Structurally similar to oxytocin (differing at only two positions), vasopressin plays critical roles in water homeostasis, blood pressure regulation, and social behavior. It acts through three receptor subtypes: V1a (vascular smooth muscle contraction, social behavior), V1b (ACTH release from pituitary), and V2 (renal water reabsorption). Synthetic vasopressin and its analogs are essential medications: desmopressin (DDAVP) for diabetes insipidus and nocturnal enuresis, vasopressin for vasodilatory shock and cardiac arrest, and terlipressin for hepatorenal syndrome. It is on the WHO List of Essential Medicines.

V1a receptors (Gq-coupled) on vascular smooth muscle mediate vasoconstriction through PLC/IP3/calcium signaling. V2 receptors (Gs-coupled) in renal collecting ducts drive aquaporin-2 (AQP2) insertion into the apical membrane via cAMP/PKA, enabling water reabsorption from urine. V1b receptors stimulate ACTH release from anterior pituitary corticotrophs. In the brain, V1a activation modulates pair bonding, social recognition, and aggression.

Diabetes Insipidus (Approved) Desmopressin (DDAVP) is the standard treatment for central diabetes insipidus, replacing deficient ADH. Vasodilatory Shock (Approved) Vasopressin is used in septic shock and cardiac arrest per ACLS guidelines. Social Behavior Research V1a receptor signaling is studied for pair bonding, social recognition, and autism spectrum disorder. Hemophilia/von Willebrand Disease (Approved) Desmopressin releases stored von Willebrand factor and Factor VIII for mild hemophilia A and vWD.

V1a/Gq/PLC/calcium for vasoconstriction. V2/Gs/cAMP/PKA/AQP2 for water reabsorption. V1b/ACTH release for stress response. Central V1a signaling for social behavior.

Water intoxication/hyponatremia (V2-mediated water retention), headache, nausea, abdominal cramps. IV vasopressin: coronary vasoconstriction, digital ischemia at high doses. Desmopressin has less vasopressor activity (V2-selective).

Vasopressin injection: store at 2-8°C or controlled room temperature. Desmopressin: nasal spray at room temperature, tablets at 25°C. The disulfide bond is essential for activity.

FDA-approved: vasopressin injection (Vasostrict) for vasodilatory shock; desmopressin (DDAVP) for diabetes insipidus, nocturnal enuresis, hemophilia. WHO Essential Medicine. Not WADA-prohibited (medical use).