Oxytocin is a mammalian neurohypophysial hormone that acts primarily as a neuromodulator in the brain.
Oxytocin plays roles in sexual reproduction, in particular during and after childbirth. It is released in large amounts after distension of the cervix and uterus during labor, facilitating birth, maternal bonding, and, after stimulation of the nipples, breastfeeding. Both childbirth and milk ejection result from positive feedback mechanisms.
Recent studies have begun to investigate oxytocin’s role in various behaviors, including orgasm, social recognition, pair bonding, anxiety, and maternal behaviors. For this reason, it is sometimes referred to as the “love hormone”. There is some evidence that oxytocin promotes ethnocentric behavior, incorporating the trust and empathy of in-groups with their suspicion and rejection of outsiders. Furthermore, genetic differences in the oxytocin receptor gene (OXTR) have been associated with maladaptive social traits such as aggressive behaviour.
Oxytocin , sometimes known as the “love molecule” or the “trust molecule” plays an important role in many processes. These include uterine contractions during childbirth, sexual arousal, lactation, puberty, orgasm, facial recognition, trust, memory formation and pair bonding.
Oxytocin is a cyclic peptide hormone with just nine amino acids in sequence (CYIQNCPLG) that also acts as a neurotransmitter in the brain where it is produced in the hypothalamus. It was the first ever polypeptide hormone to be sequenced and synthesized biochemically, work for which the American biochemist Vincent du Vigneaud was awarded the 1955 Nobel Prize in Chemistry.
Together with the neuropeptide argipressin (arginine vasopressin), it is believed to influence social cognition and behaviour. First shown in mice, recent studies have shown that also in humans simply sniffing a spray containing oxytocin increases a person’s level of trust in others.
- Lee, H.J., Macbeth, A.H., Pagani, J.H. and Young, W.S. (2009) Oxytocin: the great facilitator of life. Prog. Neurobiol. (Amsterdam, Neth.) 88, 127–151.
- du Vigneaud, V., Ressler, C., Swan, J.M., Roberts, C.W., Katsoyannis, P.G. and Gordon, S. (1953) The synthesis of an octapeptide amide with the hormonal activity of oxytocin. J. Am. Chem. Soc. 75, 4879–4880..
- Kosfeld, M., Heinrichs, M., Zak, P.J., Fischbacher, U. and Fehr, E. (2005) Oxytocin increases trust in humans. Nature 435, 673–676.
Oxytocin (ball-and-stick) bound to its carrier protein neurophysin (ribbons) based on: “Crystal structure of the neurophysin-oxytocin complex” Rose, J.P., Wu, C.K., Hsiao, C.D., Breslow, E., Wang, B.C. (1996) Nat.Struct.Biol. 3: 163-169