Evidence that the onset of seasonal anoestrus in the ewe may be independent of increasing prolactin concentrations and daylength.
Evidence that the onset of seasonal anoestrus in the ewe may be independent of increasing prolactin concentrations and daylength.
复制标题
有证据表明，母羊季节性不发情的开始可能与催乳素浓度和日照长度的增加无关。
DOI：
10.1530/jrf.0.0690041
复制
发表时间：
1983
期刊：
影响因子：
--
通讯作者：
W. Haresign
中科院分区：
文献类型：
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作者：
K. Worthy;W. Haresign
多塞特角（长繁殖季节）和威尔士山（短繁殖季节）两个品种的 9 只母羊在插入含有雌二醇 17 β 的皮下植入物后被切除卵巢。每个品种还有 9 只母羊完整存活。 1980年12月12日，将所有母羊置于8L：16D的人工光周期中。5周后，每个品种和生理状态的母羊中有一半突然转变为长日照光周期（16L：8D），而其余的则保持短日照。在改为长日照的母羊中，整个动物季节性不发情的开始时间显着提前，而在维持短日照的母羊中，繁殖季节的结束在一年中的正常时间到来。发情周期活动的这些差异反映在两种光照处理中切除卵巢、接受雌激素处理的母羊的 LH 浓度降至基础值的时间差异上。长日照下的母羊催乳素浓度立即持续升高，但短日照下的母羊催乳素浓度仍然较低。由于季节性不发情的发生发生在缺乏高水平催乳素的情况下（短日照母羊），因此得出结论，催乳素并不是产生下丘脑对雌二醇负反馈效应的季节性变化的主要媒介。结果表明，不发情可能是由于光不应性造成的。
Nine ewes of each of two breeds, Dorset Horn (long breeding season) and Welsh Mountain (short breeding season), were ovariectomized after insertion of subcutaneous implants containing oestradiol-17 beta. A further 9 ewes of each breed were left entire. All of the ewes were placed in an artificial photoperiod of 8L : 16D on 12 December 1980. After 5 weeks half of the ewes of each breed and physiological state were abruptly changed into a long-day photoperiod (16L :8D) while the rest remained in short days. The time of onset of seasonal anoestrus in entire animals was significantly advanced in ewes changed to long days, with the end of the breeding season coming at the normal time of year in ewes maintained in short days. These differences in oestrous cycle activity were reflected by differences in the time at which LH concentrations in ovariectomized, oestrogen-treated ewes on the two light treatments fell to basal values. Prolactin concentrations showed an immediate and sustained rise in ewes changed to long days, but remained low in ewes maintained in short days. Since the onset of seasonal anoestrus occurred in the absence of high levels of prolactin (in short-day ewes), it is concluded that prolactin is not the major vehicle by which seasonal changes in hypothalamic responsiveness to the negative feedback effects of oestradiol are produced. The results suggest that anoestrus may be due to photorefractoriness.