Feedback actions of estradiol on GnRH secretion during the follicular phase of the estrous cycle.
Feedback actions of estradiol on GnRH secretion during the follicular phase of the estrous cycle.
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DOI：
10.55782/ane-1996-1177
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发表时间：
1996-09
影响因子：
1.4
通讯作者：
F. Karsch;N. P. Evans
中科院分区：
文献类型：
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作者：
F. Karsch;N. P. Evans
绵羊发情周期卵泡期GnRH分泌模式的特征是：开始时间歇性分泌有显著变化（频率增加，幅度降低），随后出现大量持续分泌-排卵前GnRH峰。采用卵泡期生理模型的研究表明，雌二醇对排卵前期GnRH的释放具有深刻而复杂的反馈作用。除了诱导排卵前GnRH激增外，这些效应包括对脉冲的定量效应（刺激频率，抑制幅度）和定性效应（改变脉冲形状，刺激脉冲间分泌）。在刺激的激增，雌二醇引起垂体门静脉血中GnRH的分钟到分钟模式的高度特征性变化。最初，严格的间歇性模式让位于GnRH在脉冲之间持续升高的模式。然后，随着脉动和脉冲间分量的增强，GnRh变得非常高，并且在大部分浪涌中是可变的。从这一点上看，一个规则的和组织良好的脉冲模式是不明显的。GnRH在峰期发作时的特征性时程提供了对GnRH神经分泌系统可能的机制变化的了解。这些变化包括脉冲发生机制的定量和定性改变、GnRH神经元激增特异性群体的募集、GnRH神经元和邻近细胞的形态学改变以及GnRH从其释放部位到门静脉血管系统的递送效率或途径的变化。这些可能性，虽然未经测试和推测，为未来的研究提供了一个概念框架。
The pattern of GnRH secretion during the follicular phase of the estrous cycle of sheep is characterized by an initial marked change in episodic secretion (increased frequency and decreased amplitude) followed by a massive and sustained discharge-the preovulatory GnRH surge. Studies employing a physiological model for the follicular phase have revealed that estradiol has profound and complex feedback effects on GnRH release during the preovulatory period. These include both quantitative effects on pulses (stimulation of frequency, inhibition of amplitude) and qualitative effects (altering pulse shape, stimulating interpulse secretion), in addition to inducing a preovulatory GnRH surge. In stimulating the surge, estradiol causes a highly characteristic change in the minute-to-minute pattern of GnRH in hypophyseal portal blood. Initially, a strictly episodic pattern gives way to one in which GnRH is consistently elevated between pulses. Then, following enhancement of both pulsatile and interpulse components, GnRh becomes extremely high and variable for the majority of the surge. From this point, a regular and well organized pulse pattern is not apparent. The characteristic time course of GnRH at surge onset provides insight into possible mechanistic changes in the GnRH neurosecretory system. Such changes include quantitative and qualitative alterations in the pulse generating mechanism, recruitment of a surge specific population of GnRH neurones, morphologic alterations in GnRH neurones and neighboring cells, and changes in efficiency or route of delivery of GnRH from its site of release to the portal vasculature. These possibilities, while untested and speculative, provide a conceptual framework for future research.