NEURAL PATHWAYS FROM PHOTORECEPTORS TO THE PITUITARY

总体目标是定义假定的内源性 周年节律和光折射率在调节年繁殖中的作用 在绵羊中循环，一个模范的季节性繁殖者。具体目标是： (1)检验存在内生年际节律的假设 促性腺激素和催乳素的分泌。这将通过以下方式进行测试 卵巢完整的母羊在照相室中，将它们保持在恒定的LD 12：12或 16：8光周期与血孕酮水平的监测 并延长4年。 (2)检验存在内生昼夜节律的假设 日光周期长度在变化中的位相重置效应 黄体生成素浓度。这将通过分别曝光两组 卵巢切除、雌激素治疗的母羊到交替90天的LD 16：8和LD8：16的光周期为18个月。这两个小组将是 暴露在每个光周期中，彼此180度异相。 将监测血液中黄体生成素浓度的时间变化。 (3)确定需要哪些神经结构来表达 内生的昼夜节律。母羊将受到任何一种 松果体切除术，视交叉上核或下丘脑的病变 去传入加上假手术，然后保持在恒定的LD下 12：12或LD 16：8光周期以确定推定的内源性 节奏被打乱了 (4)确定母羊康复所需的时间 光折光性。耐光的母羊将受到 不同持续时间的“恢复”光周期，然后返回 原创的光周期。将监测发情周期的开始和停止。 (5)检测出现光屈光不正的失位。 与刺激性光周期的强度相关。在夏天 至日，母羊将突然转移到两个短日照光周期 不同的长度。黄体酮将被监测以确定其相对 光周期漂移与开始和继发性停止之间的间隔 循环。

The overall aim is to define the respective roles of a putative endogenous circannual rhythm and photorefractoriness in regulating annual reprodcutive cycles in the sheep a model seasonal breeder. Specific aims are: (1) To test the hypothesis that there are endogenous circannual rhythms of gonadotropin and prolactin secretion. This will be tested by placing ovary-intact ewes in photochambers, keeping them under constant LD 12:12 or 16:8 photoperiods and monitoring changes in blood levels of progesterone and prolacting for 4 years. (2) To test the hypothesis that there is an endogenous circannual rhythm to the phase-resetting effects of the length of daily photoperiod in altering LH concentrations. This will be tested by exposing each of two groups of ovariectomized, estrogen-treated ewes to alternating 90 day periods of LD 16:8 and LD 8:16 photoperiods for 18 months. The two groups will be exposed to each photoperiod 180 degrees out-of-phase with each other. Temporal changes in blood LH concentrations will be monitored. (3) To determine which neural structures are required for expression of the endogenous circannual rhythms. Ewes will be subjected to either pinealectomy, lesions of the suprachiasmatic nucleaus, or hypothalamic deafferentation plus the sham operations and then kept under a constant LD 12:12 or LD 16:8 photoperiod to determine if the putative endongenous rhythms are disrupted (4) To determine the time period required for the ewe to recover from photorefractoriness. Photorefractory ewes will be subjected to a "recovery" photoperiod for differing durations and then returned to the original photoperiod. Onset cessation of estrous cycles will be monitored. (5) To test the hyposthesis that onset of photorefractoriness is positively correlated to the strength of the stimulatory photoperiod. At the summer solstice, ewes will be shifted abruptly to two short-day photoperiods of differing length. Progesterone will be monitored to determine the relative intervals between photoperiod shift and onset and secondary cessation of cycles.