Photoperiodic synchronization of a circannual reproductive rhythm in sheep: identification of season-specific time cues.
Photoperiodic synchronization of a circannual reproductive rhythm in sheep: identification of season-specific time cues.
复制标题
绵羊每年繁殖节律的光周期同步：季节特定时间线索的识别。
DOI：
10.1095/biolreprod50.4.965
复制
发表时间：
1994
影响因子：
3.6
通讯作者：
Karsch,FJ
中科院分区：
文献类型：
--
作者：
Woodfill,CJ;Wayne,NL;Moenter,SM;Karsch,FJ
母羊的季节性繁殖是由内源性生殖神经内分泌活动的年周期节律产生的。一年中暴露在光周期信息中的时间只要70天就足以使节律同步。本研究进行，以确定哪些部分的光周期周期用于同步。出于这个目的，我们使用松果体切除母羊，不能在一天的长度变化的生殖反应。通过褪黑激素的输注提供了选定的光周期信息，褪黑激素是一种提供该物种白昼长度的神经内分泌代码的激素。褪黑激素根据昼夜节律模式提供。输注模式，以模仿松果体完整的母羊在四个季节之一：冬季，春季，夏季或秋季的褪黑激素分泌。在松果体切除术后的三年中，每年提供90天的输注。母羊卵巢切除，并与含有雌二醇的恒定释放硅橡胶胶囊治疗;生殖神经内分泌活动进行了监测，通过测量血清LH浓度。在没有外源性褪黑激素的情况下，大多数（19/24）松果体切除对照组表现出不同步的LH周期，表明节律是自由运行的。褪黑激素同步的节奏（这样的周期是365天，节奏的阶段是同时在动物和地球物理年的适当阶段），但不是所有的褪黑激素模式在这方面同样有效。最有效的褪黑激素模式模仿那些分泌在夏季。春季和秋季褪黑激素模式效果较差，冬季褪黑激素模式无效。这些结果支持的概念，有一个季节特异性方面的光周期的线索，同步生殖神经内分泌活动的昼夜节律的母羊。最有效的同步节奏长日照光周期线索或夏至前后感知。
Seasonal reproduction in the ewe is generated by an endogenous circannual rhythm of reproductive neuroendocrine activity. Exposure to as few as 70 days of photoperiodic information a year is sufficient to synchronize the rhythm. The present study was conducted to identify which portions of the photoperiodic cycle are utilized for synchronization. For this purpose, we used pinealectomized ewes that could not respond reproductively to changes in day length. Selected photoperiodic information was provided via infusion of melatonin, a hormone that provides the neuroendocrine code for day length in this species. Melatonin was delivered according to circadian patterns. The infusion patterns were tailored to mimic those of melatonin secretion in pineal-intact ewes during one of the four seasons: winter, spring, summer, or autumn. The infusions were provided for 90 days a year during each of the three years following pinealectomy. The ewes were ovariectomized and treated with constant-release Silastic capsules containing estradiol; reproductive neuroendocrine activity was monitored by measurement of serum concentrations of LH. In the absence of exogenous melatonin, most (19 of 24) pinealectomized controls exhibited circannual LH cycles that were not in synchrony, indicating that the rhythm was free-running. Melatonin synchronized the rhythm (such that the period was 365 days and the stages of the rhythm were both concurrent among animals and in appropriate phase with the geophysical year), but not all melatonin patterns were equally effective in this regard. The most effective melatonin patterns mimicked those of secretion during summer. Spring and autumn melatonin patterns were less effective, and winter melatonin patterns were ineffective. These results support the concept that there is a seasonal specificity with regard to the photoperiodic cues that synchronize the circannual rhythm of reproductive neuroendocrine activity in the ewe. The rhythm is synchronized most effectively by long-day photoperiodic cues perceived on or around the summer solstice.