Role of receptor trafficking in synaptic plasticity during morphine dependence

描述(申请人提供)：使用阿片类止痛剂吗啡会导致严重的耐受和依赖，这可能会导致强迫使用和滥用。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。该提案的主要目的是研究阿片受体(MOR)内吞作用和再循环在吗啡依赖中的分子作用。戒断慢性吗啡后，腹侧被盖区(VTA)多巴胺神经元释放γ-氨基丁酸(GABA)的几率增加，这是中脑回路的一部分，与药物诱导的突触可塑性密切相关。根据初步数据，长期使用吗啡后GABA释放增加的可能性与其无法促进实质性的吗啡内吞和循环有关。缺乏实质性的吗啡诱导的吗啡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，在特定的目标1中，将评估慢病毒GRK2在VTA神经元过度表达在调节吗啡内吞作用中的作用。随后慢性吗啡诱导的GABA释放和戒断行为表达的变化也将被评估。在具体目标2中，将使用电生理技术在细胞水平上研究GABA传递的适应基础。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在此过程中的作用。这些实验的结果可能会对突触可塑性的诱导和吗啡内吞作用在吗啡依赖形成过程中的作用产生有趣和新颖的见解。 公共卫生相关性：阿片剂滥用和依赖对个人和社会造成衰弱后果，是一个公共卫生问题。然而，吗啡和海洛因等鸦片类药物导致耐受和依赖的原因尚不完全清楚。在这项提议中，我们将确定在长期使用吗啡过程中改变的、调节突触传递以及阿片受体内吞和再循环的细胞底物，从而导致腹侧被盖区的可塑性，腹侧被盖区是管理阿片剂奖赏和依赖的大脑回路。

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.