Cocaine-induced adaptations in inhibitory signaling in VTA dopamine neurons

 描述(申请人提供)：毒瘾是一种慢性复发性疾病，影响着美国超过2000万人，其定义为寻求和服用毒品的强迫。我们对潜在的生物学机制的有限了解阻碍了我们成功治疗成瘾的能力。我们实验室工作的长期目标是更好地了解与成瘾有关的关键神经元群体中药物诱导适应的机制和相关性。为此，我们最近描述了可卡因对腹侧被盖区(VTA)的多巴胺(DA)神经元中G蛋白依赖的抑制信号的一过性抑制，腹侧被盖区是中皮质边缘系统的关键成分。这种新的可卡因诱导的适应需要激活D2/3DA受体(D2/3R)，并涉及G蛋白门控的内向整流K(GIRK/Kir3)通道的内在化，该通道是抑制反馈通路的关键因素，通常抑制中皮质边缘系统中的DA神经传递。本项目的主要目标是更好地了解可卡因抑制VTA DA神经元GIRK依赖信号的机制和神经生理学影响(AIM 1)，并确定DA神经元GIRK通道操作对可卡因诱导的奖赏相关行为(AIM 2)的影响。我的工作假设是，可卡因引起VTA细胞外DA水平的增加，导致VTA DA神经元D2R和GIRK依赖的急性抑制，并随后内化在该细胞类型中发现的独特的GIRK通道(GIRK2/GIRK3异构体)。可卡因诱导的对VTA DA神经元GIRK依赖信号的抑制随后促进了药物暴露下DA传递的增强，以及促进和支持成瘾相关行为的长期适应的发展。我建议使用一种跨学科的方法来测试这一工作假说的关键要素，包括脑片电生理学、体外快速扫描循环伏安法和行为分析，以及对小鼠GIRK依赖信号的药理学和神经元特异性遗传操作。这个项目的成功完成将扩大我们对药物成瘾背后的抑制细胞信号机制的理解，并将为GIRK通道操作在治疗或预防成瘾方面的潜在效用提供初步评估。

 DESCRIPTION (provided by applicant): Drug addiction is a chronically relapsing disorder affecting more than 20 million people in the United States and is defined by compulsion to seek and take drug. Our ability to successfully treat addiction is hindered by our limited knowledge of the underlying biological mechanisms. A long-term goal of work in our lab is to better understand the mechanisms and relevance underlying drug-induced adaptations in key neuron populations implicated in addiction. Toward this end, we recently described a transient cocaine-induced suppression of G protein-dependent inhibitory signaling in dopamine (DA) neurons of the ventral tegmental area (VTA), a key element in the mesocorticolimbic system. This novel cocaine-induced adaptation required activation of D2/3 DA receptors (D2/3R) and involved the internalization of G protein-gated inwardly rectifying K (GIRK/Kir3) + channels, a key contributor to inhibitory feedback pathways that normally temper DA neurotransmission in the mesocorticolimbic system. The key goals of my project are to better understand the mechanisms and neurophysiological impact underlying the cocaine-induced suppression of GIRK-dependent signaling in VTA DA neurons (AIM 1), and to determine the impact of GIRK channel manipulation in DA neurons to cocaine- induced reward-related behavior (AIM 2). My working hypothesis is that the cocaine-induced increase in extracellular DA levels in the VTA leads to the acute D2R- and GIRK-dependent inhibition of VTA DA neurons, and subsequent internalization of the unique GIRK channel (GIRK2/GIRK3 heteromer) found in this cell type. The cocaine-induced suppression of GIRK-dependent signaling in VTA DA neurons then facilitates enhanced DA transmission with subsequent drug exposure, and the development of long-term adaptations that promote and support addiction-related behaviors. I propose to test key elements of this working hypothesis using an interdisciplinary approach including brain slice electrophysiology, in vitro fast scan cyclic voltammetry, and behavioral analysis, in tandem with pharmacologic and neuron-specific genetic manipulations of GIRK- dependent signaling in mice. Successful completion of this project will expand our understanding of inhibitory cell signaling mechanisms that underlie drug addiction and will provide an initial assessment of the potential utility of GIRK channel manipulation for the treatment or prevention of addiction.