Functional Characterization of OPRM1 A118G in Nicotine Dependence

描述（由申请方提供）：大量证据表明内源性阿片系统，特别是μ阿片受体（莫尔）在滥用药物（包括尼古丁）的强化作用中起作用。μ阿片受体基因（OPRM 1 Asp 40）中的单核苷酸多态性（SNP）与戒烟能力以及尼古丁奖励和戒断症状相关。然而，这种SNP影响尼古丁依赖的确切机制仍然没有得到解决。在这个R21的应用中，我们提出了一个翻译跨物种的方法来阐明OPRM 1 Asp 40变异体在尼古丁依赖的神经生物学中的功能意义。为此，我们已经开发了一种敲入小鼠，其具有Oprm 1基因（Asp 38）中Asp 40的小鼠等价物，并且我们提供了令人信服的功能意义的初步证据。了解这种变异是否会改变小鼠和人类吸烟者对尼古丁的莫尔结合，将提高我们对基因型与尼古丁相互作用的理解，并将为阐明这种SNP改变吸烟行为的神经行为机制迈出关键的第一步。拟定的小鼠实验将：1）使用[3 H]卡芬太尼和放射自显影术确定小鼠Asp 38是否改变整个大脑中莫尔结合和信号传导的基础或尼古丁刺激变化; 2）使用条件性位置偏好和尼古丁引发的再恢复范例评价Asp 38变体对尼古丁行为反应的影响。人体实验将使用[11 C]卡芬太尼PET成像评估静脉内（IV）尼古丁与生理盐水（受试者内）对24名慢性吸烟者的莫尔结合潜力的影响，这些慢性吸烟者进行了前瞻性基因分型并按OPRM 1基因型分层。这些实验将建立一个跨物种翻译模型来表征遗传变异的功能，并将阐明尼古丁依赖的神经生物学，这是一个重要的公共卫生问题。 公共卫生相关性：在小鼠和人类中进行的拟议实验将帮助我们了解特定基因变体（OPRM 1 A118 G）与尼古丁依赖相关的机制。

DESCRIPTION (provided by applicant): A substantial body of evidence implicates the endogenous opioid system, and the mu opioid receptor (MOR) in particular, in the reinforcing effects of drugs of abuse, including nicotine. A single nucleotide polymorphism (SNP) in the mu opioid receptor gene (OPRM1 Asp40) is associated with the ability to quit smoking, as well as nicotine reward and withdrawal symptoms. However, the precise mechanism through which this SNP influences nicotine dependence remains unresolved. In this R21 application, we propose a translational cross-species approach to elucidate the functional significance of the OPRM1 Asp40 variant in the neurobiology of nicotine dependence. Toward this end, we have developed a knock-in mouse that possesses the mouse equivalent of the Asp40 in the Oprm1 gene (Asp38), and we provide compelling preliminary evidence for functional significance. Understanding whether this variant alters MOR binding in response to nicotine in mice and in human smokers will improve our understanding of genotype by nicotine interactions, and will provide a critical first step toward elucidating the neurobehavioral mechanisms through which this SNP alters smoking behavior. The proposed mice experiments will: 1) determine if the mouse Asp38 alters basal or nicotine-stimulated changes in MOR binding and signaling throughout the brain using [3H]carfentanil and autoradiography; and 2) evaluate the effect of the Asp38 variant on behavioral responses to nicotine using conditioned place preference and nicotine-primed re-instatement paradigms. The human experiment will use [11C]carfentanil PET imaging to assess the effects of intravenous (IV) nicotine versus saline (within-subject) on MOR binding potential in 24 chronic smokers genotyped prospectively and stratified by OPRM1 genotype. These experiments will establish a translational cross-species model for functional characterization of genetic variants, and will elucidate the neurobiology of nicotine dependence, a significant public health problem. PUBLIC HEALTH RELEVANCE: The proposed experiments in mice and humans will help us understand the mechanisms by which a specific gene variant (OPRM1 A118G) is associated with nicotine dependence.