Estrogen Modulation of Bursting Activity in GnRH Neurons

雌激素对 GnRH 神经元爆发活性的调节

基本信息

批准号：
6830157
负责人：
Oline Karin Rønnekleiv
金额：
$ 34.92万
依托单位：
OREGON HEALTH & SCIENCE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2004
资助国家：
美国
起止时间：
2004-01-01 至 2008-12-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): The overall objectives of this project are to ascertain the mechanisms by which 17 beta-estradiol (E2) regulates GnRH neuronal excitability. GnRH neurons are crucial for the survival of the species, and both E2 and neurotransmitters are critical for the neurosecretory properties of these neurons. However, only limited knowledge is available on the cellular mechanisms by which GnRH neurons are regulated. The recent development of transgenic mice with green fluorescent protein (EGFP)-tagged GnRH neurons has greatly facilitated studies of these important neurons. Recent evidence suggests that E2 through ERbeta acts directly on GnRH neurons, as well as indirectly through ERalpha on GABA neurons to affect GnRH production and/or release. In addition, E2 alters the potency of neurotransmitters that may directly or indirectly affect GnRH neurons. Despite this growing appreciation, E2 regulation of GnRH neurons is incompletely understood. To further explore the distinct electrical properties of GnRH neurons that govern GnRH excitability and how E2 modulates these properties, we will focus on selective ion channels and receptors based on a model for burst firing in GnRH neurons. Our working hypothesis is that E2 modulates synaptic input and ion channel function acutely through membrane signaling events and over a longer time period alters the expression of specific receptors and ion channels in GnRH neurons. These changes will enhance or inhibit GnRH neuronal activity and GnRH release depending on the steroid mileu of the female, which ultimately regulates fertility. Our Specific Aims focus on key issues regulating GnRH neurons during positive feedback of LH (GnRH) secretion: (1) To measure the mRNA expression of ATP-sensitive potassium channel subunits, and determine whether E2 alters this expression. (2) To measure the acute effects of E2 on K-ATP channel function, and determine the cellular mechanism(s). (3) To ascertain whether E2 increases alpha1-adrenergic receptor mRNA expression and protein. (4) To measure the effects of E2 on the alpha1-adrenergic inhibition of a small conductance calcium-activated K+ (SK) current that underlies the medium afterhyperpolarization. (5) To ascertain whether E2 increases the mRNA expression of calcium T-channel subunits, and increases T-channel activity leading to enhanced burst firing. These studies will provide new and important information on how estrogen alters intrinsic conductances of hypothalamic GnRH neurons and how estrogen in general modifies synaptic input and thereby facilitates distinct firing patterns in GnRH neurons, which is critical for reproductive competence.

描述（由申请人提供）：该项目的总体目标是确定 17 β-雌二醇 (E2) 调节 GnRH 神经元兴奋性的机制。 GnRH 神经元对于物种的生存至关重要，而 E2 和神经递质对于这些神经元的神经分泌特性也至关重要。然而，关于 GnRH 神经元调节的细胞机制的知识有限。最近开发的带有绿色荧光蛋白（EGFP）标记的 GnRH 神经元的转基因小鼠极大地促进了对这些重要神经元的研究。最近的证据表明，E2 通过 ERbeta 直接作用于 GnRH 神经元，并通过 ERalpha 间接作用于 GABA 神经元，从而影响 GnRH 的产生和/或释放。此外，E2 改变神经递质的效力，可能直接或间接影响 GnRH 神经元。尽管人们对 E2 的认识不断加深，但 E2 对 GnRH 神经元的调节尚不完全清楚。为了进一步探索控制 GnRH 兴奋性的 GnRH 神经元的独特电特性以及 E2 如何调节这些特性，我们将重点关注基于 GnRH 神经元爆发放电模型的选择性离子通道和受体。我们的工作假设是，E2 通过膜信号传导事件敏锐地调节突触输入和离子通道功能，并在较长时间内改变 GnRH 神经元中特定受体和离子通道的表达。这些变化将增强或抑制 GnRH 神经元活性和 GnRH 释放，具体取决于女性的类固醇环境，最终调节生育能力。我们的具体目标集中在黄体生成素（GnRH）分泌正反馈过程中调节GnRH神经元的关键问题：（1）测量ATP敏感钾通道亚基的mRNA表达，并确定E2是否改变这种表达。 (2) 测定E2对K-ATP通道功能的急性影响，并确定细胞机制。 (3)确定E2是否增加α1-肾上腺素受体mRNA表达和蛋白。 (4) 测量 E2 对构成中等后超极化的小电导钙激活 K+ (SK) 电流的 α1-肾上腺素能抑制的影响。 (5) 确定E2是否增加钙T通道亚基的mRNA表达，并增加T通道活性，从而导致爆发放电增强。这些研究将提供关于雌激素如何改变下丘脑 GnRH 神经元固有电导以及雌激素如何总体上改变突触输入从而促进 GnRH 神经元不同放电模式的新的重要信息，这对于生殖能力至关重要。