Oxytocin (1)

Oxytocin was discovered by a British pharmacologist named Henry Dale in 1909. It was first synthesised in 1953 by Vincent de Vigneaud, an American chemist who was awarded the 1955 Nobel Prize for Chemistry for this discovery, the first polypeptide hormone to be synthesised. He also synthesised the related hormone vasopressin, which controls the body's retention of water. Oxytocin is cys-tyr-ile-gln-asn-cys-pro-leu-glu, vasopressin is cys-tyr-phe-gln-asn-cys-pro-arg-glu.

Oxytocin (Greek, “quick birth”) is a mammalian hormone that also acts as a neurotransmitter in the brain.

In humans, oxytocin is thought to be released during hugging, touching, and orgasm in both sexes. In the brain, oxytocin is involved in social recognition and bonding, and may be involved in the formation of trust between people and generosity.

In women, it is released in large amounts after distension of the cervix and vagina during labor, and after stimulation of the nipples, facilitating birth and breastfeeding, respectively. Synthetic oxytocin is sold as medication under the trade names Pitocin and Syntocinon as well as generic oxytocin.


(excerpts of) Oxytocin hormone benefits and side effects by Ray Sahelian, M.D.

Oxytocin is a hormone that helps relax and reduce blood pressure and cortisol levels. Oxytocin increases pain thresholds, has anti anxiety effects, and stimulates various types of positive social interaction. In addition, it promotes growth and healing.

The nonapeptide oxytocin, originally known to stimulate labor and milk ejection, appears to play an important role stress and pain. It can induce anti-stress-like effects such as reduction of blood pressure and cortisol levels. It increases pain thresholds, exerts an anxiolytic-like effect and stimulates various types of positive social interaction. In addition, it promotes growth and healing. Repeated exposure to oxytocin causes long-lasting effects by influencing the activity of other transmitter systems, a pattern which makes oxytocin potentially clinically relevant. Oxytocin can be released by various types of non-noxious sensory stimulation, for example by touch and warmth. Ingestion of food triggers oxytocin release by activation of vagal afferents. Most likely, oxytocin can also be released by stimulation of other senses such as olfaction, as well as by certain types of sound and light. In addition, purely psychological mechanisms may trigger the release of oxytocin. This means that positive interaction involving touch and psychological support may be health-promoting. The social interaction of daily life, as well as a positive environment, continuously activate this system. In addition, various types of psychotherapy involving transfer of support, warmth and empathy are likely to induce similar effects, which thus contribute to the positive effects of these kinds of therapies.


Oxytocin receptors in the body and brain
Oxytocin is a very abundant neuropeptide exerting a wide spectrum of central and peripheral effects as neurohormone, neurotransmitter, or neuromodulator. In the central nervous system, the oxytocin gene is predominantly expressed in magnocellular neurons in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei. The magnocellular oxytocin neurons release their products into the general circulation in the neurohypophysis while the mediocellular oxytocin neurons secrete elsewhere in the CNS. Oxytocin is also produced in peripheral tissues, e.g., uterus, placenta, amnion, corpus luteum, testis, and heart. Oxytocin is a potent stimulator of spontaneous erections in rats and is involved in ejaculation. The typical actions of peripheral oxytocin are stimulation of uterine smooth muscle contraction during labor and milk ejection during lactation. Oxytocin receptors have also been identified in other tissues, including the kidney, heart, thymus, pancreas, and adipocytes.