Neurosteroid Regulation of Seizures

神经类固醇对癫痫发作的调节

• 批准号: 6723703
• 负责人: Jaideep Kapur
• 金额: $ 31.64万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-30 至 2008-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6723703
• 关键词: GABA receptor; anticonvulsants; confocal scanning microscopy; dentate gyrus; diazepam; epilepsy; furosemide; gamma aminobutyrate; hormone regulation /control mechanism; immunocytochemistry; laboratory rat; neural inhibition; neuroendocrine system; neurohormones; pregnanolone; receptor expression; zinc

DESCRIPTION (provided by applicant): Epilepsy is characterized by recurrent unprovoked seizures. Biological rhythms and external stimuli can modulate seizure frequency partly through circulating steroid hormones. Neurosteroids like allopregnanolone are synthesized in the brain from circulating steroids and have powerful anticonvulsant effects. AIIopregnanolone exerts its actions in the central nervous system by acting on GABAA receptors. Physiological concentrations of allopregnanolone (10 -30 nM) potently enhanced whole cell GABA-evoked currents in hippocampal dentate granule cells acutely isolated from naive rats. In contrast, in dentate granule cells acutely isolated from epileptic rats these physiological concentrations of allopregnanolone failed to enhance whole cell GABAA receptor currents. Whole cell GABA-A receptor currents are generated by activation synaptic and extrasynaptic GABAA receptors. In dentate granule cells of naive rats, a1 and g2 subunits are expressed at synapses while a4 and d subunits are extrasynaptic. The extrasynaptic receptors mediate tonic inhibition while synaptic receptors mediate phasic (synaptic) inhibition. The tonic inhibition is insensitive to allopregnanolone, diazepam, and sensitive to Zn2+ while synaptic inhibition is sensitive to allopregnanolone, diazepam, and insensitive to Zn2+. These preliminary findings support the hypothesis that in the hippocampal dentate granule cells of epileptic rats, there is diminished allopregnanolone modulation of GABAergic inhibition. Decreased allopregnanolone modulation is due to increased expression of alpha4 and delta subunit-containing receptors, which in epileptic rats are present extrasynaptically and in subsynaptic membrane. We will test the predictions of our hypotheses by accomplishing the following specific aims: 1) To characterize allopregnanolone, diazepam, zinc, and furosemide modulation of GABA mediated miniature inhibitory synaptic currents (mlPSCs), and of GABAA receptor mediated background tonic inhibition of hippocampal dentate granule cells of epileptic and control rats. 2) To characterize the amount and site (synaptic versus extrasynaptic) of expression of specific GABAA receptor subunits in dentate granule cells in epileptic and control rats by immunohistochemistry and immunoblot studies combined with confocal laser microscopy. Significance: These experiments are of particular relevance to understanding epilepsy-induced alterations in GABA-A receptors and their modulation by neurosteroids.

描述（由申请人提供）：癫痫的特点是反复无端发作。生物节律和外部刺激可以部分通过循环类固醇激素调节癫痫发作频率。像四氢孕酮这样的神经类固醇是在大脑中由循环类固醇合成的，具有强大的抗惊厥作用。 Allopregnanolone 通过作用于 GABAA 受体在中枢神经系统中发挥作用。生理浓度的四氢孕酮 (10 -30 nM) 有效增强了从幼稚大鼠中急性分离的海马齿状颗粒细胞中 GABA 诱发的全细胞电流。相反，在从癫痫大鼠中急性分离的齿状颗粒细胞中，这些生理浓度的四氢孕酮未能增强全细胞GABAA受体电流。全细胞 GABA-A 受体电流是通过激活突触和突触外 GABAA 受体产生的。在幼稚大鼠的齿状颗粒细胞中，a1 和 g2 亚基在突触处表达，而 a4 和 d 亚基在突触外表达。突触外受体介导强直性抑制，而突触受体介导阶段性（突触）抑制。强直抑制对别孕酮、地西泮不敏感，对 Zn2+ 敏感；而突触抑制对别孕酮、地西泮敏感，对 Zn2+ 不敏感。这些初步发现支持这样的假设：在癫痫大鼠的海马齿状颗粒细胞中，四氢孕酮对 GABA 能抑制的调节减弱。四氢孕酮调节减少是由于含有α4和δ亚基的受体表达增加，这些受体在癫痫大鼠中存在于突触外和突触下膜中。 我们将通过实现以下具体目标来测试我们假设的预测：1) 表征四氢孕酮、地西泮、锌和呋塞米对 GABA 介导的微型抑制性突触电流 (mlPSC) 的调节，以及 GABAA 受体介导的海马齿状体背景强直抑制的特征癫痫大鼠和对照大鼠的颗粒细胞。 2) 通过免疫组织化学和免疫印迹研究结合共聚焦激光显微镜来表征癫痫大鼠和对照大鼠齿状颗粒细胞中特定 GABAA 受体亚基表达的数量和部位（突触与突触外）。 意义：这些实验对于理解癫痫引起的 GABA-A 受体的改变及其神经类固醇的调节特别重要。