Every physiology student is taught that oxytocin is released from the neurohypophysis and acts on the myoepithelial cells to effect milk ejection and on the myometrium to elicit uterine contractions. Milk ejection requires the bolus release of oxytocin, by the (approximately) synchronous discharge of the magnocellular oxytocin containing neurones in the hypothalamus, and this is initiated reflexly by the suckling stimulus applied to the nipple. During parturition also, oxytocin can be released as part of a neuroendocrine reflex when the fetus stimulates sensory nerve endings during its passage through the cervix. The reflex release of oxytocin at this time greatly aids the rapid completion of the delivery process.
All of the foregoing has been known for years and some of it for decades. During this time little progress was made in identifying any clearly defined physiological role for oxytocin during the earlier stages of parturition. Indeed maturational processes in the