Central actions of estrogens: Effects of GnRH neurons

描述（由申请人提供）：15%至20%的夫妇难以怀孕;因此，生殖系统的失败影响了许多人。在女性中，了解排卵的控制对于帮助那些不孕症患者怀孕是至关重要的，而不是多胞胎，生育，并开发新的方法来防止意外怀孕，其方式与大多数人口可接受的社会习俗一致，同时最大限度地减少副作用。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。这种信号是由促性腺激素释放激素（GnRH）神经元输出的变化提供的，从一个严格的偶发性，产生开/关GnRH脉冲，驱动垂体激素释放，到一个GnRH释放持续升高数小时。雌激素启动这种GnRH激增，从而诱导促黄体生成激素（LH）激增，随后触发排卵。为了诱导GnRH激增，中枢雌二醇作用从负反馈转变为正反馈。用恒定生理水平的雌二醇（OVX+E）处理的卵巢切除（OVX）小鼠经历从负反馈到正反馈的每日转变，所述正反馈定时到亮-暗周期，允许在减少变量模型中进行机制研究。在卵巢完整的小鼠中，这种雌二醇反馈模式的转换发生在发情前期。先前在每日激增模型中的工作建立了雌二醇参与的几种机制，这些机制将导致在负反馈期间GnRH神经元的抑制和在正反馈期间这些细胞的激活。在拟议的工作中，这些发现将扩展到从神经生物学机制的还原主义调查到整个动物研究的实验，所有这些实验都旨在阐明雌二醇参与调节GnRH神经元和浪涌产生的上游神经元网络。在目的1中，我们将研究kisspeptin神经元的前腹侧脑室周围（AVPV）区域，假设调解雌二醇正反馈。我们将确定它们的输入和内在特性如何随着雌二醇和一天中的时间而变化。我们还将研究雌二醇反馈如何改变kisspeptin和GnRH神经元之间的功能连接使用配对记录在脑切片。初步数据表明，放电模式，内在特性和神经传递AVPV kisspeptin神经元的雌二醇和/或一天中的时间都改变。在目标2中，我们将研究急性应激干扰LH峰的机制。这一目标将测试被压力破坏的神经生物学机制，并使用遗传和手术方法确定效应细胞。这一目标还将扩大我们对自然循环激增的机制的了解。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，这是由性腺因素加剧。将兴奋性和抑制性传入网络的研究数据整合到现有知识中，将增加我们对雌二醇控制排卵的中枢神经元的理解。

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.