Vasopressin (AVP) and oxytocin (OT) receptors are activated by the endogenous cyclic nonapeptides vasopressin (AVP) and oxytocin (OXT). These peptides are derived from precursors which also produce neurophysins (neurophysin I for oxytocin; neurophysin II for vasopressin). Vasopressin and oxytocin differ at only 2 amino acids (positions 3 and 8). There are metabolites of these neuropeptides that may be biologically active.
