Role of receptor trafficking in synaptic plasticity during morphine dependence

描述（由申请人提供）：使用阿片类镇痛剂吗啡导致严重的耐受性和依赖性，这通常可能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，但其潜在机制尚未完全阐明。本研究的主要目的是探讨μ阿片受体（莫尔）内吞和再循环在吗啡依赖中的分子作用。戒断慢性吗啡导致腹侧被盖区（VTA）多巴胺神经元（中脑回路的一部分，与药物诱导的突触可塑性密切相关）中γ-氨基丁酸（GABA）释放的环磷酸腺苷（cAMP）依赖性增加。根据初步数据，长期使用吗啡后GABA释放的可能性增加与其不能促进大量莫尔内吞和再循环有关。缺乏大量吗啡诱导的莫尔内吞作用可能是由于G蛋白偶联受体激酶2（GRK 2）的表达减少或缺乏募集。因此，在具体目标1中，将评价VTA神经元中慢病毒GRK 2过表达在调节吗啡内吞作用中的作用。还将评价随后的慢性吗啡诱导的GABA释放和戒断行为表达的变化。在具体目标2中，将使用电生理学技术在细胞水平上研究GABA传输适应的基础。将评估戒断诱导的突触前G蛋白偶联内向整流钾（GIRK）电导的变化以及cAMP在介导该变化中的作用。这些实验的结果可能会产生有趣的和新的见解突触可塑性的诱导和莫尔内吞作用在吗啡依赖的发展。 公共卫生相关性：阿片类药物滥用和依赖对个人和社会具有削弱性后果，是一个公共卫生问题。然而，阿片类药物，如吗啡和海洛因，诱导耐受性和依赖性的原因还没有完全弄清楚。在这项提案中，我们将确定控制突触传递和μ阿片受体内吞作用和回收的细胞基质，这些基质在慢性吗啡使用期间被修改，导致腹侧被盖区的可塑性，这是一种控制阿片奖励和依赖的脑回路。

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. PUBLIC HEALTH RELEVANCE: Opiate abuse and dependence has debilitating consequences on the individual and society and is a public health problem. Yet, the reason why opiate drugs, such as morphine and heroin, induce tolerance and dependence is not completely understood. In this proposal, we will identify the cellular substrates governing synaptic transmission and mu-opioid receptor endocytosis and recycling that are modified during chronic morphine use resulting in plasticity in the ventral tegmental area, a brain circuit that governs opiate reward and dependence.