Ethanol and mesolimbic GABAergic neurons

描述(由申请人提供)：这是一项探索性的(R21)资助，旨在研究GABA能神经元在酒精成瘾中的作用。中脑边缘多巴胺(DA)系统起源于腹侧被盖区(VTA)，被认为介导了包括乙醇在内的滥用药物的强化特性。急性乙醇如何增加VTA-DA神经元的活性尚未完全阐明。VTA-DA神经元处于GABA神经元的紧张性抑制控制之下。众所周知，一些滥用药物，如阿片类药物，通过抑制GABA A神经元来兴奋VTA-DA神经元--这是一种去抑制机制。最近的体内证据表明，乙醇对VTA-GABA神经元有抑制作用。初步数据显示，乙醇对VTA-GABA神经元有抑制作用。重要的是，乙醇对GABA神经元的抑制作用比对DA神经元的兴奋作用更强。我的长期目标是确定酒精成瘾的细胞机制。本研究的目的是研究GABA神经元在VTA中介导乙醇效应的机制。中心假设是，急性乙醇主要通过解除抑制，通过抑制VTA-GABA神经元的抑制张力，增加成瘾回路中VTA-DA的释放。这项拟议的工作将结合膜片钳电生理技术和对大鼠VTA神经元的药理学测试，无论是在急性脑片上还是在急性分离的神经元上。具体目的1将验证乙醇抑制VTA-GABA神经元的假设：这将通过检测乙醇对GABA神经元的自发放电和从DA神经元记录的自发IPSCs(SIPSCs)的影响来实现。具体目的2将通过比较乙醇对DA神经元的兴奋作用和对GABA神经元的抑制作用，以及在有和没有突触输入的情况下乙醇诱导的VTA-DA细胞放电增加，来检验乙醇对GABA能抑制音的抑制作用比其对DA神经元的直接兴奋作用更强的假设。这一目的还将探索GABA神经元的抑制是否影响DA神经元的爆发放电。具体目标3将通过比较乙醇在K+通道阻滞剂(S)存在和不存在的情况下对VTA-GABA细胞的效力，来验证乙醇通过增强K+电流而抑制VTA-GABA神经元间的假说。这项研究的结果将表征之前未被充分研究的乙醇对VTA-GABA神经元的影响，以及随后对VTA-DA神经元的间接影响。这些结果将为酒精成瘾特性的新机制提供有价值的信息，并为未来的神经生物学研究奠定坚实的科学基础。

DESCRIPTION (provided by applicant): This is an exploratory (R21) grant to examine the role of GABAergic (GABA) neurons in alcohol addiction. The mesolimbic dopamine (DA) system, originating from the ventral tegmental area (VTA), is thought to mediate the reinforcing properties of drugs of abuse, including ethanol. How acute ethanol increases the activity of VTA-DA neurons has not been fully elucidated. The VTA-DA neurons are under the tonic inhibitory control of GAB A neurons. It is well established that some drugs of abuse, such as opioids, excite VTA-DA neurons by inhibiting the GAB A neurons-a mechanism of disinhibition. There is recent in vivo evidence that ethanol inhibits VTA-GABA neurons. Preliminary data indicate that ethanol inhibits VTA-GABA neurons. Importantly, ethanol inhibition of the GAB A neurons is more potent than the excitation of DA neurons. My long-term goal is to identify the cellular mechanisms of alcohol addiction. The objective of this application is to examine the mechanisms by which GAB A neurons mediate the effects of ethanol in the VTA. The central hypothesis is that acute ethanol increases VTA-DA release within the addiction circuit primarily through disinhibition, by suppression of the inhibitory tone of VTA-GABA neurons. The proposed work will combine patch-clamp electrophysiological techniques with pharmacological tests on VTA neurons of rats, either in acute brain slices or in acutely dissociated neurons. Specific aim 1 will test the hypothesis that ethanol inhibits VTA-GABA neurons: this will be done by examining the effects of ethanol on both the spontaneous firing of GABA neurons, and the spontaneous IPSCs (sIPSCs) recorded from DA neurons. Specific aim 2 will test the hypothesis that ethanol inhibition of GABAergic inhibitory tone is more potent than its direct excitatory effect on DA neurons by comparing ethanol's excitatory action on DA neurons with its inhibitory potency on GABA neurons, and by comparing the ethanol-induced increase in VTA-DA cell firing in the presence and absence of synaptic inputs. This aim will also explore whether the inhibition of GABA neurons affects the burst firing of DA neurons. Specific aim 3 will test the hypothesis that ethanol inhibits VTA-GABA inter-neurons by enhancing their K+ currents by comparing ethanol's potency on VTA-GABA cells in the absence and presence of K+ channel blocker(s). The results of this study will characterize a previously under-investigated effect of ethanol on VTA-GABA neurons, and its subsequent indirect effect on VTA-DA neurons. Such results will provide valuable information on novel mechanisms underlying the addictive properties of alcohol and a firm scientific foundation for future neurobiological studies.