Estrogen Modulation of Bursting Activity in GnRH Neurons

雌激素对 GnRH 神经元爆发活性的调节

• 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
• 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
• 来源: https://reporter.nih.gov/project-details/6830157
• 关键词: biological signal transduction; estradiol; fluorescence microscopy; gamma aminobutyrate; genetically modified animals; gonadotropin releasing factor; hormone regulation /control mechanism; hypothalamus; immunocytochemistry; in situ hybridization; ion transport; laboratory mouse; messenger RNA; neurons; polymerase chain reaction; potassium channel; radioassay; synapses; video microscopy; voltage /patch clamp

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个β-雌二醇（E2）调节GNRH神经元兴奋性的机制。 GNRH神经元对于该物种的存活至关重要，E2和神经递质对于这些神经元的神经分泌特性至关重要。但是，只有在调节GNRH神经元的细胞机制上才有有限的知识。绿色荧光蛋白（EGFP）标记的GNRH神经元的转基因小鼠的最新发展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，以及通过GABA神经元上的Eralpha间接作用，以影响GNRH产生和/或释放。此外，E2会改变可能直接或间接影响GNRH神经元的神经递质的效力。尽管人们越来越多地赞赏，但E2对GNRH神经元的调节尚未完全理解。为了进一步探索控制GNRH兴奋性的GNRH神经元的不同电性能以及E2如何调节这些特性，我们将基于基于GNRH神经元中爆发的模型的选择性离子通道和受体。我们的工作假设是，E2通过膜信号事件调节突触输入和离子通道迅速发挥作用，并且在更长的时间段内会改变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，并根据雌性的类固醇Mileu释放GNRH，最终调节生育能力。 我们的具体目的集中在调节LH（GNRH）分泌正反馈期间调节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是否改变了这种表达。 （2）测量E2对K-ATP通道功能的急性影响，并确定细胞机制。 （3）确定E2是否增加了α1-肾上腺素能受体mRNA表达和蛋白质。 （4）测量E2对小电导钙激活的K+（SK）电流的α1-肾上腺素能抑制的影响，该电流是培养基过时的培养基。 （5）确定E2是否增加了钙T通道亚基的mRNA表达，并增加了T通道活性，从而导致爆发增强。这些研究将提供有关雌激素如何改变下丘脑GNRH神经元的内在电导的新的重要信息，以及一般中雌激素如何改变突触输入，从而促进GNRH神经元中不同的发射模式，这对于生殖能力至关重要。