Role of receptor trafficking in synaptic plasticity during morphine dependence

描述（由申请人提供）：阿片类镇痛药吗啡的使用导致深刻的耐受性和依赖性，这可能经常导致强迫性使用和滥用。虽然已经确定，与其他滥用药物一样，接触吗啡会导致大脑回路的改变，但潜在的机制尚未完全阐明。本提案的主要目的是研究吗啡依赖中mu-阿片受体（MOR）内吞和再循环的分子作用。慢性吗啡戒断导致腹侧被盖区（VTA）多巴胺神经元释放γ -氨基丁酸（GABA）的可能性增加，这部分中脑回路与药物诱导的突触可塑性密切相关。根据初步数据，慢性吗啡使用后GABA释放增加的可能性与它不能促进大量的MOR内吞和再循环有关。缺乏吗啡诱导的MOR内吞作用可能是由于g蛋白偶联受体激酶2 （GRK2）的表达减少或缺乏募集。因此，在Specific Aim 1中，我们将评估VTA神经元中慢病毒GRK2过表达在吗啡内吞作用中的作用。随后慢性吗啡诱导的戒断后GABA释放和行为表达的变化也将被评估。在Specific Aim 2中，将使用电生理技术在细胞水平上研究GABA传输的适应基础。我们将评估戒断诱导的突触前g蛋白偶联内纠偏钾（GIRK）电导的变化以及cAMP在其中的介导作用。这些实验的结果可能会对突触可塑性的诱导和吗啡依赖过程中MOR内吞作用的作用产生有趣和新颖的见解。

DESCRIPTION (provided by applicant): Use of the opioid analgesic morphine results in profound tolerance and dependence, which may often lead to compulsive use and abuse. While it has been established that exposure to morphine, as with other drugs of abuse, causes modifications in brain circuits, the underlying mechanisms have not been completely elucidated. The broad objectives of this proposal are to investigate the molecular role of mu-opioid receptor (MOR) endocytosis and recycling in morphine dependence. Withdrawal from chronic morphine results in a cyclic adenosine monophosphate (cAMP)-dependent increased probability of gamma-aminobutyric acid (GABA) release in ventral tegmental area (VTA) dopamine neurons, part of the midbrain circuit strongly implicated in drug-induced synaptic plasticity. Based on preliminary data, this increased probability of GABA release after chronic morphine use is connected to its inability to promote substantial MOR endocytosis and recycling. Lack of substantial morphine-induced MOR endocytosis could be due to reduced expression or lack of recruitment of the G-protein coupled receptor kinase2 (GRK2). Therefore, in Specific Aim 1, the role of lentiviral GRK2 over-expression in VTA neurons in modulating morphine endocytosis will be evaluated. Subsequent chronic morphine-induced changes in GABA release and behavioral expression of withdrawal will also be evaluated. In Specific Aim 2, the basis for adaptations in GABA transmission will be investigated at the cellular level using electrophysiological techniques. Withdrawal-induced changes in pre-synaptic G-protein coupled inwardly rectifying potassium (GIRK) conductance and the role of cAMP in mediating the same will be evaluated. The results from these experiments are likely to yield interesting and novel insights on the induction of synaptic plasticity and the role of MOR endocytosis during development of morphine dependence.