Changes in the Ionic Basis of GABAergic Inhibition that Contribute to Post-traumatic Epilepsy

脑损伤是难治性癫痫的常见原因。因为我们不了解 潜在的病理生理学，我们不能减少医疗棘手的负担。总体 这项研究计划的目标是利用最近开发的大型动物脑回模型， 新皮质创伤后癫痫（PTE），以阐明新皮质癫痫发生的机制： GABA介导的抑制作用的离子基础的慢性损害。去抑制是一种基本的 但到目前为止，我们还没有发现慢性癫痫发作的去抑制机制。 癫痫有两个突出的线索：第一，增加GABA电导的抗惊厥药通常 不能改善PTE;第二，对人类难治性癫痫的研究发现， GABAA受体介导的膜电流（EGABA）的逆转电位的去抑制转变。 在这里，我们将测试的假设，胶质重建脑细胞外基质损伤后， 导致细胞外氯化物（Cl-0）被细胞外基质的硫酸盐部分的置换增加。 蛋白聚糖组成新的基质。为了验证这一假设，我们将使用一种大型动物 PTE模型，其中在充分表征的新皮层损伤后发生局部癫痫（项目1 大动物核心（Large Animal Core）癫痫发生的这种定位对于Cl-0变化的相关性至关重要， 网络结构和癫痫。在这个受伤的新皮层区域，我们将使用纵向双光子， 体内钙成像以测试预期来自去抑制的网络变化（项目2和 显微镜核心）。在受伤的新皮层区域，我们将使用双光子荧光寿命成像 （FLIM）和新合成的Cl-指示剂，以测试局部Cl-和细胞内氯化物的变化 (Cl-i），这将通过去极化EGABA和降低分流抑制的功效来驱动去抑制 （项目3）。这三个项目有一个共同的第三个目标：将癫痫发生（项目1）与 网络去抑制（项目2）与Cl-0和Cl-1（项目3）的慢性变化相关。 这些项目和核心将共同测试癫痫发生和医学的新机制。 这种顽固性可以通过短期抑制大脑的分解来改善。 在损伤时使用MMP抑制剂，其疗效将在项目中筛选 3，目标2.

Brain injury is a common cause of medically intractable epilepsy. Because we do not understand the underlying pathophysiology, we can’t reduce the burden of medical intractability. The overarching goal of this research program is to exploit a recently developed large animal gyrencephalic model of neocortical post-traumatic epilepsy (PTE) to elucidate a mechanism of neocortical epileptogenesis: chronic compromise of the ionic basis for GABA-mediated inhibition. Disinhibition is a fundamental element of ictogenesis, but thus far we have not found the mechanism of disinhibition in chronic epilepsy. There are two salient clues: first, anticonvulsants that increase GABA conductance often do not ameliorate PTE; and second, studies in human intractable epilepsy have found a positive, disinhibitory shift in the reversal potential for GABAA receptor-mediated membrane currents (EGABA). Here we will test the hypothesis that glial reconstruction of the brain’s extracellular matrix after injury results in increased displacement of extracellular chloride (Cl-o) by the sulfate moieties of the proteoglycans that comprise the new matrix. To test this hypothesis, we will employ a large-animal PTE model in which local epileptogenesis occurs after well-characterized neocortical injury (Project 1 and Large Animal Core). This localization of epileptogenesis is critical for correlation of changes in Cl-o, network structure, and epilepsy. In this injured neocortical area, we will use longitudinal 2-photon in vivo calcium imaging to test for the network changes expected from disinhibition (Project 2 and Microscopy Core). In the injured neocortical area, we will use 2-photon Fluorescence Lifetime Imaging (FLIM) and newly-synthesized Cl- indicators to test for changes in the local Cl-o and intracellular chloride (Cl-i ) that would drive disinhibition by depolarizing EGABA and reducing the efficacy of shunting inhibition (Project 3). The 3 projects have a common third aim: to correlate epileptogenesis (Project 1) with network disinhibition (Project 2) that are associated with chronic changes in Cl-o and Cl-i (Project 3). Together, these Projects and Cores will test a novel mechanism of epileptogenesis and medical intractability that could be ameliorated by short-term inhibition of the disassembly of the brain’s extracellular matrix at the time of injury using MMP inhibitors whose efficacy will be screened in Project 3, Aim 2.