Neurophysin 2 specifically binds vasopressin. Vasopressin has a direct antidiuretic action on the kidney, it also causes vasoconstriction of the peripheral vessels. Acts by binding to vasopressin receptors (V1bR/AVPR1B, V1aR/AVPR1A, and V2R/AVPR2) (By similarity). Interacts with vasopressin receptors V1bR/AVPR1B (Ki=85 pM), V1aR/AVPR1A (Ki=0.6 nM) and V2R/AVPR2 (Ki=4.9 nM) (By similarity). Interacts with oxytocin receptor (OXTR) (Ki=110 nM) (By similarity). Belongs to the vasopressin/oxytocin family.