GABA Receptor Subunit Plasticity in Epilepsy

描述（由申请人提供）：GABAA受体（GABAR）的改变可能在颞叶癫痫中发挥关键作用。现在人们认识到，特定GABAR亚基的变化可以改变易患癫痫的脑区的抑制特征，而不一定会产生大量或普遍的抑制丧失。δ亚基将是这些研究的重点，因为含有该亚基的GABAR似乎是唯一的塑料，在GABA介导的紧张性抑制中发挥重要作用，并且可能是神经类固醇在某些脑区域（如齿状回）中的主要生物靶点。广泛的假设是δ亚基表达和定位的变化可能通过改变紧张性抑制和对神经类固醇的反应性来影响癫痫发作的易感性。将在匹鲁卡品治疗的复发性癫痫发作小鼠模型中以及在给予合成神经活性类固醇后研究变化。光镜和电镜免疫组织化学方法的组合将用于鉴定δ亚基和相关GABAR亚基（包括α 4和γ 2）表达和定位的变化。以下问题将得到解决：1）δ亚基表达的减少是否会导致癫痫小鼠模型中其他GABAR亚基（如γ 2）亚细胞定位的改变？2)在正常和癫痫动物中表达高水平δ亚基的中间神经元的形态和功能特征是什么？3)在齿状回的神经元中，什么GABAR亚基与δ亚基一起定位？4)δ亚单位表达是否因长期服用神经活性类固醇加奈索酮而改变？在所有研究中，重点将放在评估海马结构中主细胞和中间神经元中GABAR亚基变化之间的潜在差异上。形态学研究结果将与本计划项目其他组成部分中的GABARs生理和生化研究相关。这些研究可以确定可能有助于癫痫发作活动的新型GABAR可塑性，也可能为癫痫和相关疾病的药物治疗提供细胞特异性靶点。

DESCRIPTION (provided by applicant): Alterations in GABAA receptors (GABARs) are likely to play pivotal roles in temporal lobe epilepsy. It is now recognized that changes in specific GABAR subunits could alter the characteristics of inhibition in seizure-prone brain regions without necessarily producing a massive or generalized loss of inhibition. The delta subunit will be the focus of these studies because GABARs that contain this subunit appear to be uniquely plastic, play an important role in GABA-mediated tonic inhibition and may be major biological targets of neurosteroids in some brain regions such as the dentate gyrus. The broad hypothesis is that changes in delta subunit expression and localization could influence seizure susceptibility by altering tonic inhibition and responsiveness to neurosteroids. Changes will be studied in a pilocarpine-treated mouse model of recurrent seizures and following administration of a synthetic neuroactive steroid. A combination of light and electron microscopic immunohistochemical methods will be used to identify changes in expression and localization of the delta subunit and related GABAR subunits that include alpha4 and gamma2. The following questions will be addressed: 1) Does a decrease in delta subunit expression lead to alterations in the subcellular localization of other GABAR subunits such as gamma2 in a mouse model of epilepsy? 2) What are the morphological and functional characteristics of interneurons that express high levels of the delta subunit in normal and epileptic animals? 3) What GABAR subunits are localized with the delta subunit in neurons of the dentate gyrus? 4) Is delta subunit expression altered by chronic administration of the neuroactive steroid ganaxolone? In all studies, emphasis will be placed on evaluating potential differences between GABAR subunit changes in principal cells and interneurons in the hippocampal formation. The morphological findings will be related to physiological and biochemical studies of GABARs in other components of this program project. The studies could identify new types of GABAR plasticity that could contribute to seizure activity and might also suggest cell-specific targets for pharmacological treatment of epilepsy and related disorders.