Effects of development and prenatal androgen exposure on GnRH neuron intrinsic properties

项目摘要 促性腺激素释放激素(GnRH)神经元构成生殖控制的最终中枢通路 功能，以搏动性方式释放促性腺激素释放激素。低频促性腺激素释放激素脉冲促进卵泡分泌- 促黄体生成素(FSH)，而高频促性腺激素释放激素(GnRH)有助于黄体生成素的分泌 (Lh)。这些荷尔蒙分泌模式的紊乱可能会导致不育或不育。多囊性 卵巢综合征(PCOS)，特别是高雄激素血症，是一种疾病，在这种疾病中 这些荷尔蒙释放模式会导致生育能力受损。具体地说，持续的高频黄体生成素，以及 推测GnRH，脉搏是高雄激素血症多囊卵巢综合征的标志。研究神经内分泌方面 可能导致这种疾病，这项拟议的工作使用了产前雄激素(PNA)小鼠模型。PNA 小鼠概括了高雄激素血症多囊卵巢综合征妇女的许多神经内分泌表型， 包括生殖周期中断、促黄体生成素脉冲频率升高和睾丸素升高。的研究 GFP鉴定的三周龄PNA雌性GnRH神经元的动作电位放电活动是 低于来自控件的单元格中的。相反，成年PNA小鼠细胞中的GnRH神经元活性增加 相对于控件。这是一个奇怪的观察，因为GnRH中的GABA能传递是兴奋的 在这两个发育时间点，神经元的数量都增加了。在3周大的PNA雌性中，GnRH神经元 与对照相比，对本地GABA应用的激发响应减少，但没有变化 无论是通过GABAA受体的电流的反转电位，还是在这些受体的基底膜电位中 细胞。总而言之，这些观察结果表明，电压门控通道中发生的变化 PNA小鼠GnRH神经元对幼鼠兴奋性突触输入增加的补偿作用 这些变化在成年人身上不会保持，从而导致多动。我早期的数据显示促性腺激素释放激素神经元 兴奋性和动作电位特征在不同组之间可以是相似的，但具有不同的潜在因素 显影和PNA处理后的离子电导特性。这个项目的第一个目标是 测试电压门控钾(K)电流如何在神经元对突触的反应中发挥重要作用 在这些组之间，输入和产生动作电位是不同的。我们的发现被用来产生 有助于这一解释的钾电流的计算模型第二个目标将使用 动态钳夹法检测来自对照组和PNA小鼠的GnRH神经元对不同的 模拟了我们以前的工作和/或电流注入中的GABA电导。我们还将测试如何建模 钾电流与记录的促性腺激素释放激素神经元的自然环境相互作用以解释 回应。这个项目的完成将提供对GnRH神经元的内在属性的洞察，如何 这些变化在典型的发育和PNA治疗期间发生，潜在地提供了对病因的洞察 并为我提供了成功成为一名独立科学家所需的培训。

Project Summary Gonadotropin-releasing hormone (GnRH) neurons form the final central pathway for the control of reproductive function, releasing GnRH in a pulsatile manner. Low frequency GnRH pulses favor the secretion of follicle- stimulating hormone (FSH), whereas high frequency GnRH pulses favor the secretion of luteinizing hormone (LH). Disruptions to the secretory patterns of these hormones can result in subfertility or infertility. Polycystic ovary syndrome (PCOS), and in particular hyperandrogenemic PCOS, is a disorder in which disruptions to these hormone release patterns result in impaired fertility. Specifically, sustained high frequency LH, and presumably GnRH, pulses are a hallmark of hyperandrogenemic PCOS. To study neuroendocrine aspects that may contribute to this disorder, the proposed work uses a prenatally androgenized (PNA) mouse model. PNA mice recapitulate many neuroendocrine phenotypes reported in women with hyperandrogenemic PCOS, including disrupted reproductive cycles, elevated LH-pulse frequency and increased testosterone. Studies of GFP-identified GnRH neurons from three-week-old PNA females revealed that action potential firing activity is lower than in cells from controls. In contrast, GnRH neuron activity is increased in cells from adult PNA mice relative to controls. This was a curious observation as GABAergic transmission, which is excitatory in GnRH neurons, was increased at both of these developmental timepoints. In 3-wk old PNA females, GnRH neurons have a reduced firing response to local GABA application compared to controls, but there is no change in either reversal potential for current through the GABAA receptor or in the basal membrane potential of these cells. Together these observations suggest the postulate that changes occur in voltage-gated channels of GnRH neurons from PNA mice to compensate for increased excitatory synaptic input in young mice but that these changes are not maintained in adults, leading to hyperactivity. My early data indicate that GnRH neuron excitability and action potential characteristics can be similar among the groups, but have different underlying ionic conductance characteristics as a result of development and PNA treatment. The first aim of this project tests how voltage-gated potassium (K+) currents, which play a large role in how neurons respond to synaptic inputs and generate action potentials, are altered among these groups. Our findings we be used to generate computational models of potassium currents that will assist in this interpretation The second aim will use dynamic clamp to test if GnRH neurons from control vs PNA mice respond differently to representative trains of simulated GABA conductances from our previous work and/or current injection. We will also test how modelled potassium currents interact with the native milieu of recorded GnRH neurons to account for differences in response. Completion of this project will provide insight into the intrinsic properties of GnRH neurons, how these change during typical development and with PNA treatment, potentially providing insight into the etiology of PCOS and providing me with the training required to successfully become an independent scientist.