Functional Characterization of OPRM1 A118G in Nicotine Dependence

描述(由申请人提供)：大量证据表明，内源性阿片系统，特别是Mu阿片受体(MOR)参与了包括尼古丁在内的滥用药物的强化作用。MU阿片受体基因(OPRM1 Asp40)的单核苷酸多态性(SNP)与戒烟能力、尼古丁奖赏和戒断症状有关。然而，这种SNP影响尼古丁依赖的确切机制仍未解决。在这个R21的应用中，我们提出了一种跨物种的翻译方法来阐明OPRM1 Asp40变体在尼古丁依赖的神经生物学中的功能意义。为此，我们开发了一种敲入小鼠，它拥有相当于OPRM1基因中的Asp40(Asp38)的小鼠，我们为其功能意义提供了令人信服的初步证据。了解这种变异是否会改变小鼠和人类吸烟者对尼古丁的反应，将提高我们对尼古丁相互作用的基因型的理解，并将为阐明这种SNP改变吸烟行为的神经行为机制提供关键的第一步。拟进行的小鼠实验将：1)使用[~3H]卡芬太尼和放射自显影技术确定小鼠Asp38是否改变了基础或尼古丁刺激的MOR结合和整个大脑信号的变化；以及2)使用条件性位置偏爱和尼古丁启动的重复陈述范式评估Asp38变体对尼古丁行为反应的影响。这项人体实验将使用[11C]卡芬太尼PET成像来评估静脉注射(IV)尼古丁与生理盐水(在受试者内部)对24名慢性吸烟者MOR结合潜力的影响，这些吸烟者按OPRM1基因分层进行了前瞻性的基因分型。这些实验将为基因变异的功能表征建立一个跨物种的翻译模型，并将阐明尼古丁依赖的神经生物学，这是一个重大的公共卫生问题。 公共卫生相关性：在小鼠和人类身上进行的拟议实验将帮助我们了解特定基因变体(OPRM1A118G)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.