Neuroendocrine Control of the Ovarian Cycle of the Rat
摘要：
The ovine estrous cycle in ewes is controlled by a complex interaction between cues from the external environment and internal hormonal signals. Environmental factors influence ovulation rate and determine whether or not estrous cycles occur, but are not directly involved in the events of the estrous cycle. Instead, these endocrine events reflect a coordinated hormonal communication among the brain, pituitary, ovaries, and uterus. The primary coordinator of this communication within the ewe is progesterone, which controls the timing of the major endocrine events of the estrous cycle. Superimposed on these internal events are four major environmental cues. First, changes in nutrition influence the number of healthy follicles and thus ovulation rate. Second, stressors inhibit follicular phase events, delaying the occurrence of ovulation. Finally, photoperiod and pheromones control when estrous cycles occur. Long-day photoperiods, by activating inhibitory neural systems, actively suppress ovarian cycles, but these inhibitory effects of photoperiod can be disrupted by introduction of pheromones from the ram. The external cues appear to influence ovarian cycles largely by controlling the negative feedback action of stradiol. Inhibitory photoperiods induce an ovulation by increasing estradiol negative feedback, and pheromones trigger ovulation by blocking estradiol negative feedback. Moreover, with the return of ovulatory cycles, progesterone concentrations increase, and resume control of the hypothalamic pulse generator and hence the occurrence of ovulation.
展开
DOI：
10.1016/B978-012515400-0/50048-8
被引量：
年份：
2006
通过文献互助平台发起求助，成功后即可免费获取论文全文。
相似文献
参考文献
引证文献
引用走势
站内活动
辅助模式
引用
文献可以批量引用啦~
欢迎点我试用！
