CHAPTER 44 – Neuroendocrine Control of the Ovarian Cycle of the Sheep

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 determine whether or not cycles occur, but are directly involved events of cycle. Instead, these endocrine reflect coordinated communication among brain, pituitary, ovaries, uterus. primary coordinator this within ewe progesterone, which controls timing major Superimposed on four environmental cues. First, changes nutrition number healthy follicles thus rate. Second, stressors inhibit follicular phase events, delaying occurrence ovulation. Finally, photoperiod pheromones control when occur. Long-day photoperiods, activating inhibitory neural systems, actively suppress ovarian cycles, effects can be disrupted introduction ram. appear to largely controlling negative feedback action stradiol. Inhibitory photoperiods induce an increasing estradiol feedback, trigger blocking feedback. Moreover, with return ovulatory progesterone concentrations increase, resume hypothalamic pulse generator hence