Oxytocin: Pharmacologic properties, physiological effects and role in pregnancy

Oxytocin is a nine amino acid CNS neuropeptide. It is produced in the supraopticand paraventricular nuclei of the hypothalamus and is mainly released from theneurohypophysis and nerve terminals in response to multiple physiological stimuli.Oxytocin exerts its biological action by binding to the oxytocin receptor in the targetorgans which triggers an increase in the cellular calcium ions. Oxytocin has a main rolein pregnancy, labor, lactation, and maternal behavior; however, it is also involved withother physiological and pathological functions such as sexual activity, penile erection,ejaculation, osteoporosis, diabetes, cancer, social bonding, and stress. In the reproductivesystem oxytocin participates in parturition via its effect on the myometrium to induceuterine contractions. This action is regulated by several agents including sex steroids andoxytocin itself. The paracrine and autocrine mechanisms regulating oxytocin and itsreceptor within the fetoplacental-uterine unit are central to the control of uterinecontractions and parturition. Oxytocin also participates in lactation through its effects onthe mammary glands. Interestingly, oxytocin might participate in regulating maternalbehavior and bonding via its effect on the dopaminergic reward pathways in response tosocial cues. Oxytocin's characteristics have led to the development of effective oxytocin receptoragonists and antagonists which are in use for labor induction and preterm labor arrestrespectively. Moreover, oxytocin administration has been shown to be effective inpreventing and treating postpartum hemorrhage.In this review we will focus on the roll of oxytocin in pregnancy and lactation. Wewill highlight its physiological effects as well as mechanism of action and regulation inpregnancy, parturition, the third phase of labor and lactation. We will also review the roleof oxytocin analogs in those processes. Finally, we will address possible future leads ofinvestigation.