Oxytocin causes contraction of the smooth muscle of the uterus and of the mammary glands. The oxytocin-neurophysin 1 precursor is processed into oxytocin and neurophysin 1, which specifically binds to oxytocin. Oxytocin is available as Pitocin (Parke-Davis) and Syntocinon (Sandoz) to artificially speed or induce labor.Human: H-Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2 (Cys1-Cys6) or H-CYIQNCPLG-NH2 (Cys1-Cys6)