Enhanced excitation and epilepsy with chloride channel dysfunction

神经网络的兴奋性是由兴奋和抑制之间的平衡定义的。当这种平衡被打破有利于兴奋，网络变得超兴奋。这一观察结果构成了确定癫痫相关病理的一般指导原则。考虑到这一点，重大的努力已被导向了解的分子特性，定义兴奋性和抑制性神经传递。脑中抑制的主要来源是神经递质γ-氨基丁酸（GABA）与GABAA受体亚型的结合，GABAA受体亚型起配体门控氯离子通道的作用。这种GABA能抑制反过来取决于跨神经元膜存在的氯化物浓度梯度。CLC 2氯离子通道亚型是负责建立这种梯度的几种通道之一。最近，发现几种人类特发性全身性癫痫（IGE）与CLC 2突变有关。丘脑是一种皮质下结构，是产生与IGE相关的癫痫发作活动的关键组成部分。然而，CLC 2在丘脑中的功能尚不清楚。我提出的项目的目标是了解CLC 2中断如何促进丘脑网络的过度兴奋。我的初步结果表明，CLC 2功能障碍增强了体外丘脑网络活动的兴奋性。这种网络增强是由选择性增加突触兴奋到丘脑神经元的亚型。虽然令人惊讶地观察到在CLC 2破坏期间改变的兴奋性传递，但这种效应可能使丘脑网络过度兴奋。我设计了几个实验来确定这种增强的突触兴奋的介导机制。其中一些实验依赖于技术--脑电图记录/解释、局部脑灌注、成像技术--我将从同意培训我的顾问那里学习这些技术。

Neural network excitability is defined by the balance between excitation and inhibition. When this balance is disrupted in favor of excitation, networks become hyperexcitable. This observation constitutes a general guiding principle for determining the pathologies associated with epilepsy. With this in mind, significant effort has been directed towards understanding the molecular properties that define excitatory and inhibitory neurotransmission. A major source of inhibition in the brain results from the binding of the neurotransmitterY-aminobutyric acid (GABA) to GABAA receptor subtypes, which function as ligand-gated chloride channels. This GABAergic inhibition, in turn, depends on the chloride concentration gradient present across neuronal membranes. The CLC2 chloride channel subtype is one of several channels responsible for establishing this gradient. Recently, it was discovered that several human idiopathic generalized epilepsies (IGEs) are associated with CLC2 mutations. The thalamus, a subcortical structure, is a critical component for the generation of seizure activity associated with the IGEs. However, the function of CLC2 in the thalamus is unknown. The goal of my proposed project is to understand how CLC2 disruptions promote network hyperexcitability in the thalamus. My preliminary results indicate that CLC2 dysfunction enhances the excitability of thalamic network activity in vitro. This network enhancement is paralleled by a selective increase in synaptic excitation onto a subtype of thalamic neurons. While surprising to observe altered excitatory transmission during CLC2 disruption, this effect likely renders thalamic networks hyperexcitable. I have designed several experiments to determine the mechanism mediating this enhanced synaptic excitation. Several of these experiments rely on techniques - EEG recording/interpretation, local brain perfusion, imaging techniques - that I will learn from consultants that have agreed to train me.