Functional Integrity of the Oxytocin-Releasing Reflex in Goats: Dependence on Estrogen1

作者：J.S. Roberts · 发表于：Endocrinology · 年份：1973 · DOI：10.1210/endo-93-6-1309 · 被引用次数：28 · 研究领域：Neuroendocrine regulation and behavior、Menstrual Health and Disorders、Hypothalamic control of reproductive hormones

To examine the hypothesis that a recent history of exposure to estrogen is essential if vaginal distention stimuli are to effect an increase in the rate of release of oxytocin from the neurohypophysis, the relative responsiveness of this distention reflex was assessed in intact goats and in ovariectomized goats bearing Silastic capsules containing 17β-estradiol. In intact, seasonally responsive animals, vaginal distention increased the level of oxytocin in jugular venous blood from a resting value of 2.6 ± 0.4 to 77.2 ± 15.8 μU/ml plasma (mean it SEM). After ovariectomy, the reflex retained function only if the animals were treated with estradiol from the time of surgery. If not treated, the stimulated increase fell significantly to 33.5 ± 4.9 nμ/ml 10 to 24 days after the operation. Later, the reflex became completely unresponsive and remained so indefinitely in the absence of estradiol therapy. When estradiol therapy was instituted in such cases, responsiveness returned slowly. Only after 3 months of continuous exposure to estradiol were all subjects responsive. Stimulation at this time generated an average oxytocin titer of 19.5 ± 2.3 μU/ml plasma, significantly above the resting level of 2.5 ± 0.6 μU/ml. This degree of responsiveness was maintained until summer, when, despite an evidently continuous supply of estradiol, the reflex lost its reactivity. Only with the arrival of winter, when the reflex in intact animals exhibits renewed responsiveness following a refractory ...