Oxytocin (OT) is a 9-amino acid peptide that is synthesized primarily in the hypothalamic neurons, specifically the magnocellular oxytocin neurons in the supraoptic and paraventricular nuclei and is secreted by the posterior pituitary gland. It is also secreted from other tissues, such as the ovaries and testes. Circulating OT is important during parturition and lactation. In the pregnant uterus, oxytocin and the oxytocin receptor play a major part for uterine contractility and the induction of labor. OT is also involved in complex social behaviors such as affiliation, sexual behavior, social recognition, stress buffering, aggression, and trust.