Relevance and plasticity of inhibitory metabotropic signaling in reward circuits

项目总结 滥用药物具有增强腹侧被盖区多巴胺(DA)神经传递的能力 (VTA)至下游靶区，包括内侧前额叶皮质(MPFC)和伏核(NAC)。 对VTA DA神经元的直接刺激是强化的，并且足以触发分子、细胞和 定义成瘾的行为适应。药物滥用的作用受到抑制性G蛋白的反对 奖赏回路中的信号通路。精神刺激剂可减弱VTA中抑制性G蛋白信号转导 DA神经元和前皮质5/6层锥体神经元(PLC)通过选择性地减少细胞 G蛋白门控内向整流钾通道(GIRK)的表面表达GIRK的基因抑制 药物幼稚小鼠的通道活动唤起了一些细胞适应和典型的行为结果 与反复接触毒品有关，支持GIRK渠道至关重要和可被利用的观点 先天成瘾障碍的贡献者。该项目的目标是使用新的工具和方法 深入了解药物对GIRK依赖信号传导的调节机制 并研究与增强GIRK通道活性相关的治疗潜力。 神经元和/或通道子类型特定的方式。具体目标有两个：(1)调查招聘 GIRK依赖反馈对VTA DA神经元的治疗潜力。功能丧失突变体，包括 DA神经元中缺乏GIRK通道的小鼠提示VTA DA中发现的独特的GIRK通道亚型 神经元是对滥用药物的行为敏感性的关键调节因素。此前提将使用以下工具进行测试 VTA DA中选择性增强或抑制GIRK依赖信号的交叉病毒操作 神经元，然后在非或有和反应-或有测试中进行行为评估，包括 可卡因。平行地，独特的VTA DA神经元GIRK通道的新激活剂的治疗潜力 子类型将被评估。最后，将使用体内光遗传方法来测试相性VTA DA 在VTA DA神经元中，活动足以参与和抑制GIRK依赖的信号。(2)揭示 PLC中依赖GIRK的前馈抑制电路的机制和相关性。虽然在 最初的项目阶段确定了5/6层PLC锥体神经元中依赖GIRK的信号是一种 成瘾障碍，这个障碍是如何以及何时被利用的还不清楚。光发生和化学发生途径 将被用来测试VTA DA神经元相激活唤起前馈的工作模型 涉及5/6层PLC GABA中间神经元D1R依赖激活的抑制电路 相邻锥体神经元对DA依赖的平行激活。拟议的研究还测试了 预测该前馈电路的重复接合足以触发对GIRK的抑制 5/6层PLC锥体神经元的通道活动及其GIRK依赖信号的增强 神经元对可卡因的成瘾作用具有韧性。

PROJECT SUMMARY Drugs of abuse share an ability to enhance dopamine (DA) neurotransmission from the ventral tegmental area (VTA) to downstream targets, including the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc). Direct stimulation of VTA DA neurons is reinforcing and sufficient to trigger the array of molecular, cellular, and behavioral adaptations that define addiction. The actions of drugs of abuse are opposed by inhibitory G protein signaling pathways in the reward circuitry. Psychostimulants can weaken inhibitory G protein signaling in VTA DA neurons and layer 5/6 pyramidal neurons of the prelimbic cortex (PLC), via a selective reduction in the cell surface expression of G protein-gated inwardly rectifying K+ (GIRK) channels. Genetic suppression of GIRK channel activity in drug-naïve mice evokes some of the cellular adaptations and behavioral outcomes typically associated with repeated drug exposure, supporting the outlook that GIRK channels are critical and exploitable contributors to innate addiction barriers. The goals of this project are to use new tools and approaches to gain refined insights into the mechanisms mediating the recruitment of GIRK-dependent signaling by drugs of abuse, and to investigate the therapeutic potential associated with enhancing GIRK channel activity in a neuron- and/or channel subtype-specific fashion. There are two specific aims: (1) To probe the recruitment and therapeutic potential of GIRK-dependent feedback to VTA DA neurons. Loss-of-function mutants, including mice lacking GIRK channels in DA neurons, suggest that the unique GIRK channel subtype found in VTA DA neurons is a key regulator of behavioral sensitivity to drugs of abuse. This premise will be tested using intersectional viral manipulations to enhance or suppress GIRK-dependent signaling selectively in VTA DA neurons, followed by behavioral assessments in non-contingent and response-contingent tests involving cocaine. In parallel, the therapeutic potential of novel activators of the unique VTA DA neuron GIRK channel subtype will be evaluated. Lastly, an in vivo optogenetic approach will be used to test whether phasic VTA DA activity is sufficient to engage and suppress GIRK-dependent signaling in VTA DA neurons. (2) To reveal the mechanisms and relevance of a GIRK-dependent feedforward inhibitory circuit in the PLC. Although work in the initial project period established that GIRK-dependent signaling in layer 5/6 PLC pyramidal neurons is an addiction barrier, how and when this barrier is engaged is unclear. Optogenetic and chemogenetic approaches will be used to test the working model that phasic activation of VTA DA neurons evokes a feedforward inhibitory circuit involving the D1R-dependent activation of layer 5/6 PLC GABA interneurons, which tempers the parallel DA-dependent activation of adjacent pyramidal neurons. The proposed studies also test the predictions that repeated engagement of this feedforward circuit is sufficient to trigger the suppression of GIRK channel activity in layer 5/6 PLC pyramidal neurons, and that strengthening GIRK-dependent signaling in these neurons confers resilience to the addictive effects of cocaine.