Oxytocin and Vasopressin

Abstract

There can no longer be any doubt that oxytocin controls milk ejection, and it is generally accepted that milk ejection is mediated mainly by a humoral mechanism—the release of oxytocin in response to suckling (Bisset, 1968). It is also clear that suckling not only initiates the milk ejection reflex, but it is also necessary for maintenance of milk secretion in the lactating rat. The salient point would then be the problem whether synthesis of milk by the cells of the alveolar epithelium and the passage of milk from the cytoplasm of the alveolar epithelial cells into the alveolar lumen are dependent on oxytocin as assumed by Selye (1934 a, b) and Selye, Collip and Thompson (1934). It was concluded years ago that involution of the mammary glands in the rat after weaning is due not to accumulation of secreted milk, but to withdrawal of the suckling stimulus, and it was suggested that suckling stimulated also the secretion of prolactin from the anterior pituitary. Thus, Petersen (1944) as well as Benson and Folley (1956), Benson (1960) and Benson, Cowie and Tindal (1958) advanced the idea that the oxytocin released by suckling constitutes a stimulus for prolactin release. This hypothesis was based on their success in retarding the involution of the lactating mammary gland by injections of oxytocin.KeywordsMammary GlandConditioned StimulusAlveolar Epithelial CellPosterior PituitaryProlactin ReleaseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.