TESTOSTERONE REGULATION OF GNRH NEURONAL ACTIVITY

下丘脑-垂体-性腺轴的协调活动和分泌对男性生殖至关重要。视前区/下丘脑区少量弥漫分布的神经元的激活导致促性腺激素释放激素(GnRH)脉冲性地分泌到垂体门静脉系统中，GnRH刺激脑垂体黄体生成素和卵泡刺激素，分别驱动睾酮的分泌和精子的生成。睾丸激素在脑下丘脑和脑下垂体的水平上都有反馈抑制作用。控制睾酮负反馈作用的准确的视前/下丘脑靶点和潜在机制尚不清楚。睾酮可能直接作用于GnRH神经元本身或通过突触前GABA能机制发挥作用。一般的假设是，在男性，睾酮通过直接和/或通过GABA介导的突触前机制降低GnRH神经元的活性，对黄体生成素的分泌起负反馈作用。这项建议利用GnRH-绿色荧光蛋白转基因小鼠模型，结合可视化的细胞贴附和全细胞膜片钳记录和单细胞RT-PCR技术来验证这一假设。具体目标1将确定睾酮是否直接改变GnRH神经元的活性膜特性和放电模式。具体目标2将确定睾酮是否改变GnRH神经元上的GABA能突触传递。特异性目标3将确定睾酮是否改变已鉴定的GnRH神经元中雄激素受体、GnRH和GABAA受体亚单位的mRNA水平

The coordinated activity and secretions of the hypothalamic-pituitary-gonadal axis are vital to male reproduction. Activation of a small, diffuse population of neurons in the preoptic/hypothalamic area result in the pulsatile secretion of gonadotropin-releasing hormone (GnRH) into the hypophysial-portal vasculature which stimulates luteinizing hormone and follicle-stimulating hormone from the pituitary, driving testosterone secretion and spermatogenesis, respectively. Testosterone exerts feedback inhibition at both the levels of the pituitary and hypothalamus. The precise preoptic/hypothalamic target site and underlying mechanisms that govern the negative feedback actions of testosterone are unknown. The possibility exists that testosterone may act directly on the GnRH neuron, itself or through a pre-synaptic GABAergic mechanism. The general hypothesis is that in males, testosterone exerts its negative feedback action on luteinizing hormone secretion by reducing GnRH neuronal activity either directly and/or through a GABA-mediated pre-synaptic mechanism. This proposal utilizes the GnRH-green fluorescent protein transgenic mouse model in combination with visualized cell-attached and whole-cell patch clamp recordings and single-cell RT PCR techniques to test this hypothesis. Specific Aim 1 will determine whether testosterone directly alters the active membrane properties and firing pattern of GnRH neurons. Specific Aim 2 will determine if testosterone alters GABAergic synaptic transmission on GnRH neurons. Specific Aim 3 will determine if testosterone alters androgen receptor, GnRH and GABAA receptor subunit mRNA levels in identified GnRH neurons