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。现在已经认识到，特定GABAR亚基的变化可以改变癫痫易发脑区域的抑制特征，而不一定会导致大规模或全面性的抑制丧失。Delta亚基将是这些研究的重点，因为包含该亚基的GABA受体似乎是独特的可塑性，在GABA介导的紧张性抑制中发挥重要作用，并可能是神经类固醇在某些大脑区域(如齿状回)的主要生物学靶点。广泛的假设是，Delta亚单位的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易感性。将研究匹罗卡品治疗反复发作的小鼠模型以及在给予合成神经活性类固醇后的变化。结合光学和电子显微镜免疫组织化学方法将被用来确定Delta亚基和相关的GABAR亚基的表达和定位的变化，包括Alpha4和Gamma2。以下问题将被解决：1)在癫痫小鼠模型中，Delta亚单位表达的减少是否会导致其他GABAR亚单位的亚细胞定位的改变？2)在正常和癫痫动物中，高水平表达Delta亚单位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，哪些GABAR亚单位与Delta亚单位一起定位？4)长期服用神经活性类固醇Ganaxolone会改变Delta亚单位的表达吗？在所有研究中，重点将放在评估GABAR亚单位在主细胞和海马结构中的中间神经元变化之间的潜在差异上。这些形态研究结果将与本计划项目其他组成部分中的GABAR的生理和生化研究相关。这些研究可以识别可能导致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.