Opiate Sensitivity: The Function and Significance fo GIRK3

G蛋白门控内向整流钾离子通道（GIRK）介导突触后抑制效应 许多神经递质和相关药物的滥用。我研究的长期目标是了解 GIRK通道如何影响与抑制性神经递质调制相关的行为 信号通路最近正向和反向遗传学研究的结果表明， GIRK 3亚基影响小鼠对阿片类药物关键行为效应的敏感性，包括镇痛， 奖励和依赖。虽然GIRK 3 cDNA在十多年前就被克隆出来了，但精确的 该亚基的功能仍然存在争议。本提案的目标是了解如何以及在何处 GIRK 3影响小鼠对阿片类药物行为效应的敏感性。我们目前的假设是 GIRK 3与其他GIRK亚基组装形成相对不敏感的功能通道 GABA（B）依赖性抑制。事实上，初步研究表明，GIRK 3的缺失使多巴胺 腹侧被盖区神经元对GABA（B）受体激活更敏感。观察到的灵敏度降低， 因此，缺乏GIRK 3的小鼠对阿片类药物的行为影响可能反映出对阿片类药物的敏感性增加。 腹侧被盖区多巴胺能神经元对GABA（B）依赖性抑制提供了局部GABA能 中间神经元。因此，需要相对高水平的阿片类药物来解除VTA多巴胺的抑制 这一过程被认为是阿片类药物的运动刺激和强化作用的基础， 吗啡这一工作假设和概念框架将使用多学科 在两个具体目标中描述的方法：#1）测量GIRK 3对GABA（B）的贡献。 依赖性抑制GIRK 3的功能将通过测量GABA（B）依赖性的 培养神经元中的GIRK电流在多次遗传操作后被设计为干扰水平 和/或GIRK 3的功能。#2）探索GIRK 3和VTA对阿片诱导行为的贡献。 将采用立体定位方法将药物和遗传试剂递送至小鼠VTA，然后 在已建立的测试范例中评估阿片诱导的行为。

G protein-gated inwardly-rectifying potassium ion channels (GIRK) mediate the postsynaptic inhibitory effect of many neurotransmitters and related drugs of abuse. The long-term goal of my research is to understand how GIRK channels influence behaviors associated with the modulation of inhibitory neuretransmitter signaling pathways. Recent findings from both forward and reverse genetic studies have suggested that the GIRK3 subunit influences the sensitivity of mice to key behavioral effects of opiates, including analgesia, reward, and dependence. Though the GIRK3 cDNA was cloned more than a decade ago, the precise function of this subunit remains controversial. The goal of this proposal is to understand how and where GIRK3 influences the sensitivity of mice to the behavioral effects of opiates. Our current working hypothesis is that GIRK3 assembles with other GIRK subunits to form functional channels that are relatively insensitive to GABA(B)-dependent inhibition. Indeed, preliminary studies show the loss of GIRK3 renders dopamine neurons of the VTA more sensitive to GABA(B) receptor activation. The observed decreased sensitivity of mice lacking GIRK3 to the behavioral effects of opiates could reflect, therefore, an increased sensitivity of VTA dopamine neurons to the tonic GABA(B)-dependent inhibition provided by local GABAergic interneurons. Consequently, relatively high levels of opiates would be required to disinhibit VTA dopamine neurons, a process thought to underlie the motor stimulatory and reinforcing effects of opiates such as morphine. This working hypothesis and conceptual framework will be tested using multi-disciplinary approaches described in two specific aims: #1) To measure the contribution of GIRK3 to GABA(B)- dependent inhibition in neurons. The function of GIRK3 will be evaluated by measuring GABA(B)-dependent GIRK currents in cultured neurons following multiple genetic manipulations designed to perturb the level and/or function of GIRK3. #2) To probe the contribution of GIRK3 and the VTA to opiate-induced behaviors. Stereotaxic methods to deliver drugs and genetic reagents to the mouse VTA will be employed, followed by assessments of opiate-induced behavior in an established testing paradigm.