NEURAL PATHWAYS FROM PHOTORECEPTORS TO THE PITUITARY

总的目的是确定一个假定的内源性 昼夜节律与光不应性在调节周年生殖中的作用 在羊的周期一个模型季节性繁殖。 具体目标是： (1)为了检验存在内源性的年周期节律的假设， 促性腺激素和催乳素分泌。 这将通过放置 卵巢完整的母羊在光室，保持他们在恒定LD 12：12或 16：8光周期和监测孕酮的血液水平的变化 4年来， (2)为了检验存在内源性年周期节律的假设， 日光周期长度的相位重置效应 LH浓度。 这将通过暴露两组中的每一组进行测试， 卵巢切除，雌激素治疗的母羊，以交替90天的LD周期 16：8和LD 8：16光周期18个月。 两组将在 暴露于彼此相位相差180度的每个光周期。 将监测血液LH浓度的时间变化。 (3)为了确定哪些神经结构是表达 内源性年周期节律 母羊将受到 松果体切除术、视交叉上核或下丘脑病变 切断传入神经加假手术，然后保持恒定的LD 12：12或LD 16：8光周期，以确定假定的内源 节奏被打乱 (4)为了确定母羊恢复所需的时间 光不应性 将对光不敏感的母羊进行 “恢复”光周期不同的持续时间，然后返回到 原始光周期 将监测发情周期的开始停止。 (5)为了验证光不应性的发病是积极的假设， 与刺激光周期的强度相关。 在夏季 冬至，母羊将突然转移到两个短日照， 不同的长度。 将监测预后，以确定相对 光周期转换和发病之间的时间间隔和二次停止 自行车.

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.