Chronic Intermittent Ethanol and Kv4.2 Channels

 描述（由申请人提供）：大量饮酒与海马功能障碍相关。有证据表明，酗酒者中依赖于露营的认知障碍是导致高复发率和治疗效果差的一个因素。慢性酒精暴露重塑神经元突触，这些结构和功能的神经适应已牵连在学习和记忆缺陷。然而，我们对酒精相关认知能力下降的神经机制的认识存在很大差距。在海马CA1区锥体神经元中，由Kv4.2a亚基组成的电压依赖性钾通道在远端树突中富集，是阈下瞬时A型钾电流（ISA）的基础。Kv4.2通道通过调节突触整合和可塑性来关键地调节神经元信号传导。先前的研究表明，Kv4.2的表面表达是通过与一组称为K+通道相互作用蛋白（KChIP）的蛋白质相互作用来促进的。新出现的证据表明，Kv4.2通道和NMDA受体之间存在功能性偶联，这可能对可塑性至关重要，并受KChIP 3调节。我们的初步数据表明，慢性乙醇处理的器官型海马脑片培养物减少Kv4.2通道功能和表面表达，并增强CA1锥体神经元远端顶端树突的反向传播动作电位（bAP）诱发的Ca2+瞬变。此外，慢性乙醇显着降低KChIP 3的表达和增加NMDA受体的表达。在成年大鼠中，慢性间歇性乙醇（CIE）暴露下调Kv4.2通道的表达和损害的表现依赖于大脑的任务。因此，我们的初步数据已确定Kv4.2通道和KChIP3作为有前途的分子靶点，其是慢性酒精暴露后CA1锥体神经元异常信号处理的基础。我们设计了一组全面而集中的研究来测试这一提议的总体假设，即慢性乙醇暴露导致Kv4.2通道功能降低和NMDA受体上调，从而增强bAP信号传导、异常可塑性和海马功能障碍。本研究拟采用生物化学、切片电生理、多电极记录、光遗传学和病毒载体技术等多方面的方法来验证以下假设：目的1）验证CIE通过调节KChIP 3双向改变海马Kv 4.2通道和NMDA受体表达的假设;目的2）在急性脑片制备中验证CIE降低Kv4.2通道的表达和功能并改变发放时间依赖性突触可塑性的假设;和目的3）确定CIE是否改变海马的认知功能并在体内诱导异常的海马可塑性。这些研究将推进我们对乙醇相关突触可塑性和认知功能损伤的神经机制的认识，并确定新的治疗靶点，以更有效地治疗酒精中毒和酒精相关问题。

 DESCRIPTION (provided by applicant): Heavy alcohol consumption is associated with hippocampal dysfunction. Evidence suggests that hippocampal-dependent cognitive impairments in alcoholics are a contributing factor in high relapse rates and poor treatment outcomes. Chronic alcohol exposure remodels glutamatergic synapses, and these structural and functional neuroadaptations have been implicated in learning and memory deficits. However, there is a substantial gap in our knowledge about the neural mechanisms that underlie alcohol-associated cognitive decline. In CA1 pyramidal neurons of the hippocampus, voltage-dependent potassium (Kv) channels comprised of Kv4.2 a subunits are enriched in distal dendrites and underlie the subthreshold transient A-type K+ current (ISA). Kv4.2 channels function to critically regulate neuronal signaling by modulating synaptic integration and plasticit. Previous work has shown that surface expression of Kv4.2 is promoted through interaction with a group of proteins called K+ channel interacting proteins (KChIPs). Emerging evidence suggests that there is a functional coupling between Kv4.2 channels and NMDA receptors that may be critical for plasticity and is regulated by KChIP3. Our preliminary data demonstrate that chronic ethanol treatment of organotypic hippocampal slice cultures reduces Kv4.2 channel function and surface expression and enhances Ca2+ transients evoked by back-propagating action potentials (bAPs) in distal apical dendrites of CA1 pyramidal neurons. In addition, chronic ethanol significantly reduced KChIP3 expression and increased NMDA receptor expression. In adult rats, chronic intermittent ethanol (CIE) exposure down-regulates Kv4.2 channel expression and impairs performance on hippocampal-dependent tasks. Thus, our preliminary data have identified Kv4.2 channels and KChIP3 as promising molecular targets that underlie aberrant signal processing in CA1 pyramidal neurons in following chronic alcohol exposure. We have designed a comprehensive yet focused set of studies to test the overarching hypothesis of this proposal that the reduction in Kv4.2 channel function and up-regulation of NMDA receptors by chronic ethanol exposure contributes to enhanced bAP signaling, aberrant plasticity and hippocampal dysfunction. The proposed studies involve a multifaceted approach that involves biochemistry, slice electrophysiology, multielectrode recording, optogenetics, and viral vector technologies to test the following hypotheses: Aim 1) Test the hypothesis that CIE bidirectionally alters expression of Kv4.2 channels and NMDA receptors in the hippocampus through modulation of KChIP3; Aim 2) Test the hypothesis that CIE reduces expression and function of Kv4.2 channels and alters spike timing- dependent synaptic plasticity in the acute slice preparation; and Aim 3) Determine whether CIE alters the cognitive function of the hippocampus and induces aberrant hippocampal plasticity in vivo. These studies will advance our knowledge of the neural mechanisms contributing to ethanol-associated impairments in synaptic plasticity and cognitive function and identify novel therapeutic targets for more effective treatment of alcoholism and alcohol-related problems.