oxytocin

oxytocin (ŏksĭtōˈsĭn) [key], hormone released from the posterior lobe of the pituitary gland that facilitates uterine contractions and the milk-ejection reflex. The structure of oxytocin, a cyclic peptide consisting of nine amino acids, was determined in 1953 and in the same year it was synthesized in the laboratory. Both oxytocin and antidiuretic hormone are biosynthesized in the hypothalamus of the brain and travel down neuronal axons to the posterior pituitary, where they accumulate prior to release. Stimuli that elicit the release of oxytocin include childbirth, suckling, and coitus; the uterine contractions that result may facilitate either childbirth or the ascent of spermatozoa through the fallopian tubes. Oxytocin may also play a role in the initiation of labor. The milk-ejection response occurs only in females immediately after childbirth. The role of oxytocin in males is unknown.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

More on oxytocin from Fact Monster:

  • Vincent du Vigneaud - du Vigneaud, Vincent du Vigneaud, Vincent , 1901–78, American biochemist, b. Chicago. He was ...
  • peptide - peptide peptide, organic compound composed of amino acids linked together chemically by peptide ...
  • mammary gland - mammary gland mammary gland, organ of the female mammal that produces and secretes milk for the ...
  • pituitary gland: Pituitary Hormones - Pituitary Hormones The tissues in the anterior lobe consist of extensive vascular areas ...
  • hormone - hormone hormone, secretory substance carried from one gland or organ of the body via the ...

See more Encyclopedia articles on: Biochemistry