Effects of Chronic Alcohol Exposure on Synaptic Plasticity in the Prefrontal Cort

描述（由申请人提供）：前额叶皮层（PFC）对高级认知功能和复杂行为的组织至关重要，包括与成瘾有关的行为。尽管有明确的临床证据表明，长期饮酒会改变PFC的活动和功能，但令人惊讶的是，人们对分子和细胞水平上的潜在变化知之甚少。尽管前额叶-边缘回路中谷氨酸能神经传递的改变与成瘾的发展有关，但关于慢性酒精如何诱导PFC内的异常可塑性，我们几乎一无所知。要了解酒精诱导的PFC功能变化，需要了解兴奋性突触传递特性的变化，特别是NMDA受体功能的变化。这一应用的首要假设是，慢性乙醇暴露诱导NMDA受体的稳态增加，这将影响反向传播动作电位和局部Ca2+尖峰之间的相互作用，这是尖峰时间依赖的可塑性所必需的，这是突触可塑性的生理相关模型。这种变化可能改变整合特性和突触可塑性，并可能代表酒精依赖下PFC锥体神经元的病理神经适应。因此，长时间酒精暴露后，NM.D.AR活性的增加可能导致异常的可塑性，这可能导致PFC反应抑制的丧失，这可能是饮酒行为的基础。我们提供了支持这一观点的初步数据。在目前的探索性R21应用中，我们将在成年未用药小鼠和长期暴露于酒精的小鼠的急性脑切片中检测乙醇诱导的PFC突触可塑性的变化。小鼠的酒精消耗量将在有限获取模式下测量，并通过将动物以慢性间歇性方式暴露于酒精蒸气中诱导依赖性。目的1将使用电流钳记录来评估NMDA受体的稳态变化对突触可塑性的影响。因此，我们将研究spike-timing dependent plasticity （STDP；由EPSPs与反向传播动作电位配对诱导的可塑性），以研究长期增强（LTP）或抑郁（LTD）的幅度和诱导阈值的变化。目的1.1将确定主要影响（即酒精暴露动物STDP的改变）及其在停药后1周内的持续情况。Aim 1.2将测试NMDA受体的变化是否会改变STDP诱导的频率依赖性。在Aim 2中，我们将使用电流钳记录和高分辨率Ca2+成像的组合来研究改变的Ca2+内流通过基底树突（树突Ca2+尖峰）的NMDA受体是否为STDP的假设变化提供了一种机制。Aim 2.2检验了另一种假设，即在Aim 1中，电压门控Ca2+通道是酒精导致STDP假设变化的主要靶点。

DESCRIPTION (provided by applicant): The prefrontal cortex (PFC) is of critical importance for higher order cognitive functions and the organization of complex behaviors, including those related to addiction. In spite of clear clinical evidence that chronic alcohol consumption alters the activity and function of the PFC, surprisingly little is known about the underlying changes at the molecular and cellular level. Although altered glutamatergic neurotransmission in prefrontal- limbic circuits has been implicated in the development of addiction, virtually nothing is known regarding how chronic alcohol may induce aberrant plasticity within the PFC. An understanding of the alcohol-induced changes in PFC function requires knowledge of the changes in the properties of excitatory synaptic transmission and specifically NMDA receptor function. The over-arching hypothesis of this application is that chronic ethanol exposure induces homeostatic increases in NMDA receptors, which will affect the interplay between backpropagating action potentials and localized Ca2+-spikes that are required for spike timing-dependent plasticity, a physiologically relevant model of synaptic plasticity. Such changes could alter integrative properties and synaptic plasticity and may represent pathological neuroadaptations of PFC pyramidal neurons underlying alcohol dependence. Thus, the increased NM.D.AR activity after prolonged ethanol exposure may result in aberrant plasticity, which could contribute to a loss of response inhibition in the PFC that may underlie alcohol drinking behavior. We provide preliminary data that supports this idea. In the current exploratory R21 application, we will examine ethanol-induced changes in the synaptic plasticity of the PFC in acute brain slices from adult drug-naive mice and mice chronically exposed to alcohol. Alcohol consumption of mice will be measured in a limited-access paradigm and dependence will be induced by exposing animals to alcohol vapor in a chronic-intermittent fashion. Aim 1 will use current-clamp recordings to assess the effects of the homeostatic changes at the NMDA receptor on synaptic plasticity. Therefore, we will study spike-timing dependent plasticity (STDP; plasticity induced by pairing EPSPs with backpropagating action potentials) to study changes in the magnitude and induction threshold of long term potentiation (LTP) or depression (LTD). Aim 1.1 will establish the main effect (i.e., alterations in STDP in alcohol exposed animals) and its persistence over 1 week of withdrawal. Aim 1.2 will test whether changes at NMDA receptors shift the frequency dependence of the induction of STDP. In Aim 2 we will use a combination of current clamp recordings and high resolution Ca2+ imaging to investigate whether altered Ca2+ influx through NMDA receptors in basal dendrites (dendritic Ca2+ spikes) provides a mechanism for the hypothesized changes in STDP. Aim 2.2 tests the alternative hypothesis that voltage-gated Ca2+ channels are a main target of alcohol responsible for the hypothesized changes in STDP in Aim 1. PUBLIC HEALTH RELEVANCE: The prefrontal cortex is critically involved in the regulation of higher order cognitive functions and disturbances in these processes may underlie a loss of control over alcohol drinking behavior. The experiments in this project will use an animal model of alcohol addiction to study changes in glutamatergic synaptic transmission and NMDA receptor function in the prefrontal cortex. These studies will provide insights into the mechanisms that underlie synaptic plasticity during the development and maintenance of addiction to alcohol.