Oxytocin is luteolytic in the rhesus monkey (Macaca mulatta)

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Abstract
Oxytocin (10 mi.u./.mu.l per h) or vehicle(0.5% chlorobutanol in saline, 1 .mu.l/h) was chronically infused directly into the corpus luteum of normally cyclic rhesus monkeys, by means of an Alzet pump-ovarian cannula system. Infusion of oxytocin (n = 6) or vehicle (n = 5) began 6 days after the preovulatory estradiol surge, and daily peripheral blood samples were taken. Oxytocin caused a significant (P < 0.05) decrease in progesterone, beginning 1 day after treatment, and estradiol after 4 days; progesterone and estradiol remained significantly depressed until menstruation. Peripheral LH [luteinizing hormone] concentrations remained unchanged. The duration of the luteal phase, menstrual cycle and the onset of menses from the initiation of oxytocin infusion were significantly (P < 0.01) shorter when compared to those of vehicle-treated controls. Oxytocin can induce functional luteolysis in the primate. Oxytocin of luteal origin may play a role in spontaneous luteolysis.