Central actions of estrogens: Effects of GnRH neurons

描述(由申请人提供)：15%到20%的夫妇受孕困难；生殖系统的故障因此影响到许多人。在女性中，了解排卵控制对于帮助那些患有不孕症的人单胎怀孕而不是多胞胎怀孕至关重要，对于开发新的方法以符合大多数人可接受的社会习俗的方式防止意外怀孕，同时将副作用降至最低至关重要。这项建议的目的是增加我们对最终导致排卵的中枢神经信号产生的理解。这一信号是由促性腺激素释放激素(GnRH)神经元的输出从严格地间歇性地产生驱动垂体激素释放的GnRH脉冲的输出转变为GnRH释放持续数小时的。雌二醇会引发促性腺激素释放激素(GnRH)分泌激增，进而导致黄体生成素(LH)分泌激增，进而引发排卵。为了诱导GnRH激增，中枢雌二醇的作用从负反馈切换到正反馈。用生理水平恒定的雌二醇(OVX+E)治疗的卵巢切除(OVX)小鼠每天都会经历从负反馈到正反馈的转变，这是根据明暗循环的时间安排的，从而允许在减少变量的模型中进行机制研究。在卵巢完整的小鼠中，雌二醇反馈模式的这种转换发生在发情前期。以前在每日电涌模型中的工作确立了雌激素参与的几种机制，这些机制将导致负反馈期间GnRH神经元的抑制和正反馈期间这些细胞的激活。在这项拟议的工作中，这些发现将被扩展到从神经生物学机制的简化论研究到整体动物研究的各种实验，所有这些实验都旨在阐明雌二醇参与调节GnRH神经元和电涌产生的上游神经元网络。在目标1中，我们将研究前腹侧脑室周围区(AVPV)中的Kispeptin神经元，该神经元被认为是介导雌二醇正反馈的。我们将确定它们的输入和内在特性如何随雌二醇和一天中的时间变化。我们还将使用脑片上的配对记录来研究雌激素反馈如何改变Kispeptin和GnRH神经元之间的功能连接。初步数据表明，雌激素和/或一天中的时间都改变了AVPV Kispeptin神经元的放电模式、固有特性和神经传递。在目标2中，我们将研究急性应激扰乱黄体生成素激增的机制。这一目标将测试被压力破坏的神经生物学机制，并使用遗传学和外科方法确定效应细胞。这一目标还将扩大我们对自然周期激增背后的机制的了解。初步数据表明，应激抑制浪涌产生的昼夜模式，应激肽促肾上腺皮质激素释放激素抑制GnRH神经元，性腺因子加剧了这种情况。将兴奋性和抑制性传入神经网络的研究数据整合到现有的知识中，将增加我们对雌激素对排卵的中枢神经元控制的理解。

DESCRIPTION (provided by applicant): Between 15 and 20% of couples have difficulty conceiving; failures of the reproductive system thus affect many individuals. In females, understanding the control of ovulation is critical for helping those with infertility conceive singe, as opposed to multiple, births, and for developing novel methods to prevent unwanted pregnancy in manners that are consistent with the acceptable social mores of most of the population, while minimizing side effects. The goal of this proposal is to increase our understanding of the generation of the central neural signal that ultimately leads to ovulation. This signal is provided by a shift in output of gonadotropin-releasing hormone (GnRH) neurons from one that is strictly episodic, producing on/off GnRH pulses that drive pituitary hormone release, to one in which GnRH release is continuously elevated for several hours. Estradiol initiates this GnRH surge, which induces the luteinizing hormone (LH) surge that subsequently triggers ovulation. To induce the GnRH surge, central estradiol action switches from negative feedback to positive feedback. Ovariectomized (OVX) mice treated with constant physiological levels of estradiol (OVX+E) undergo daily shifts from negative to positive feedback that are timed to the light-dark cycle, allowing mechanistic studies in a reduced variable model. In ovary-intact mice, this switch in estradiol feedback mode occurs on proestrus. Previous work in the daily surge model established several mechanisms engaged by estradiol that would lead to suppression of GnRH neurons during negative feedback and activation of these cells during positive feedback. In the proposed work, these findings will be extended with experiments that range from reductionist investigation of neurobiological mechanisms to whole animal studies, all aimed at elucidating the upstream neuronal networks engaged by estradiol to regulate GnRH neurons and surge generation. In Aim 1, we will study kisspeptin neurons in the anteroventral periventricular (AVPV) region, postulated to mediate estradiol positive feedback. We will determine how their inputs and intrinsic properties change with estradiol and time of day. We will also study how estradiol feedback alters functional connectivity between kisspeptin and GnRH neurons using paired recordings in brain slices. Preliminary data indicate firing pattern, intrinsic properties and neurotransmission to AVPV kisspeptin neurons are altered both by estradiol and/or time of day. In Aim 2, we will study the mechanisms by which an acute stress disrupts the LH surge. This aim will test the neurobiological mechanisms that are disrupted by stress, and determine effector cells using genetic and surgical approaches. This aim will also expand our knowledge of mechanisms underlying the surge to the natural cycle. Preliminary data indicate a diurnal pattern to stress inhibition of surge generation, that the stress peptide corticotropin- releasing hormone inhibits GnRH neurons and that this is exacerbated by gonadal factors. Integration of the data resulting from the study of an excitatory and an inhibitory afferet network into existing knowledge will increase our understanding of the central neuronal control of ovulation by estradiol.