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）神经元形成控制生殖的最终中枢通路。 功能，以脉动方式释放GnRH。低频GnRH脉冲有利于卵泡分泌- 刺激激素（FSH），而高频率GnRH脉冲有利于促黄体激素的分泌 （LH）.这些激素分泌模式的中断可导致生育力低下或不育。多囊 卵巢综合征（PCOS），特别是高雄激素血症PCOS，是一种紊乱， 这些激素释放模式导致生育能力受损。具体来说，持续高频LH， 推测GnRH脉冲是高雄激素血症PCOS的标志。研究神经内分泌方面， 可能导致这种疾病，拟议的工作使用产前雄激素化（PNA）小鼠模型。PNA 小鼠重现了许多在患有高雄激素血症PCOS的女性中报道的神经内分泌表型， 包括生殖周期紊乱、LH脉冲频率升高和睾酮增加。研究 GFP鉴定的来自三周龄PNA雌性的GnRH神经元显示，动作电位放电活动是 低于对照组的细胞。相反，成年PNA小鼠的细胞中GnRH神经元活性增加 相对于对照。这是一个奇怪的观察，因为GABA能传递在GnRH中是兴奋性的。 神经元，在这两个发育时间点增加。在3周龄PNA雌性中，GnRH神经元 与对照组相比，对局部GABA应用的放电反应降低，但在 通过GABAA受体的电流的逆转电位或这些受体的基底膜电位 细胞总之，这些观察结果表明，变化发生在电压门控通道的假设， 从PNA小鼠的GnRH神经元，以补偿增加兴奋性突触输入的年轻小鼠，但 这些变化在成年人中无法维持，导致多动症。我的早期数据表明， 兴奋性和动作电位的特点可以是相似的组之间，但有不同的基础 离子电导特性作为发展和PNA处理的结果。这个项目的第一个目标 测试了电压门控钾（K+）电流，它在神经元如何响应突触刺激中起着重要作用。 输入和产生动作电位，在这些组中发生变化。我们的研究结果，我们被用来产生 钾电流的计算模型，这将有助于这种解释的第二个目标将使用 动态钳以测试来自对照与PNA小鼠的GnRH神经元是否对代表性的 模拟GABA电导从我们以前的工作和/或电流注入。我们还将测试如何建模 钾电流与记录的GnRH神经元的自然环境相互作用，以解释 反应这个项目的完成将提供深入了解GnRH神经元的内在特性，如何 这些变化在典型的发展过程中，并与PNA治疗，潜在地提供了深入了解病因 PCOS的治疗，并为我提供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.