title: Evidence for a physiological role for oxytocin in the control of prolactin secretion.
abstract: The presence of oxytocin (OT) in neuronal elements of the external layer of the median eminence and in hypophysial portal plasma suggests a role for the peptide in the control of anterior pituitary function. We have reported previously that OT stimulates PRL release in vitro; therefore, we attempted to establish evidence for a physiological PRL-releasing role for OT. Plasma OT levels rose significantly just before the PRL surges occurring during a suckling stimulus in lactating rats (10 min after pup reinstatement vs. 15 min for PRL) and 48 h after estrogen injection in ovariectomized (OVX) rats (at 1200 h vs. 1300 h). Dispersed anterior pituitary cells harvested from lactating female rats and OVX estrogen-primed rats released PRL in a specific, significant, and dose-related fashion when perifused in vitro with incubation medium containing 10(-7)-10(-9) M OT, doses similar to levels found previously in hypophysial portal plasma. Infusion of antiserum specific for OT into lactating females before pup reinstatement and into estrogen-primed OVX rats 2 h before the expected release of endogenous OT delayed and significantly reduced subsequent PRL surges compared to levels in saline-or normal rabbit serum-infused rats; however, PRL release was not completely abolished. These data indicate that OT plays a physiological role in the hypothalamic control of PRL secretion and further suggest the importance of multiple factors in coordinated regulation of PRL release.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007116:Immunization, Passive; D007774:Lactation; D010052:Ovariectomy; D010121:Oxytocin / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D004958:Estradiol; D010121:Oxytocin; D011388:Prolactin