Brain and Behavioral Effects of PENK Gene Manipulation in Rat Nucleus Accumbens

描述（由申请人提供）：大麻是青少年最常使用的非法药物，接触大麻通常早于使用“重型”药物和精神疾病。这类数据似乎支持有争议的“门户”假说，即大麻是走向滥用其他药物的垫脚石。尽管有强有力的流行病学证据表明青少年时期使用大麻与后来的药物滥用之间存在关联，但早期使用大麻与随后的药物滥用脆弱性之间几乎不存在一对一的神经生物学关联。可重复的动物数据表明，青春期大麻暴露增强了成年海洛因自我管理行为，并导致前脑啡肽原（PENK）的离散改变，这是一种对奖励和享乐状态很重要的基因，位于大脑皮层核（Acb）中，这是一个与边缘相关的大脑区域，对奖励至关重要。拟议的工作将直接测试早发性大麻使用的PENK紊乱与使用其他非法药物的进展之间是否存在因果关系。病毒介导的基因转移（PENK过表达）和RNA干扰（PENK敲低）将被用作研究与药物滥用相关的行为和神经化学状态的遗传方法。具体目标1将确定是否直接操纵PENK基因的Acb壳改变海洛因自我管理的行为。通过研究PENK的遗传操作是否会使用体内微透析改变Acb壳中阿片类药物诱导的多巴胺水平，将确定与奖励相关的大脑区域中神经递质的干扰（具体目标2）。为了表征可能导致与PENK遗传操作相关的行为和神经化学差异的特定分子改变，将分析大脑中与阿片类、DA能和大麻素神经系统相关的基因和受体的表达（特定目标3）。药物滥用是一个重大的公共卫生问题，了解诱发药物滥用障碍的风险因素对预防和治疗这些疾病至关重要。总之，该项目将提供关于在发育期间接触大麻是否存在长期影响的见解，以证实神经生物学“门户”假说，如果是这样，将有助于确定影响成年后药物滥用脆弱性的青春期潜在风险因素。

DESCRIPTION (provided by applicant): Marijuana is the illicit drug most frequently used by teenagers, and exposure to cannabis normally predates the use of "heavy" drugs and psychiatric disorders. Such data appear to support the controversial "gateway" hypothesis of cannabis as a stepping stone towards abuse of other drugs. Despite strong epidemiological evidence of an association between cannabis use during adolescence and later drug abuse, few one-to-one neurobiological correlations between early cannabis use and subsequent drug abuse vulnerability exist. Reproducible animal data has shown that cannabis exposure during adolescence potentiated adult heroin self-administration behavior and caused discrete alterations of preproenkephalin (PENK), a gene important for reward and hedonic state, in the nucleus accumbens (Acb), a limbic-related brain area central to reward. The proposed work will directly test whether there is a causal link between PENK disturbance seen with early-onset cannabis use and progression to the use of other illicit drugs. Virus-mediated gene transfer (PENK overexpression) and RNA interference (PENK knockdown) will be used as genetic approaches to study the behavioral and neurochemical states associated with drug abuse. Specific Aim 1 will determine whether direct manipulation of the PENK gene in the Acb shell alters heroin self-administration behavior. Disturbances of neurotransmitters in brain areas linked to reward will be identified by studying whether genetic manipulation of PENK alters opiate-induced dopamine levels in the Acb shell using in vivo microdialysis (Specific Aim 2). To characterize specific molecular alterations that could underlie behavioral and neurochemical differences observed in association with genetic manipulation of PENK, brains will be analyzed for expression of genes and receptors linked to the opioid, DAergic, and cannabinoid neural systems (Specific Aim 3). Substance abuse is a major public health issue, and understanding risk factors predisposing to drug abuse disorders will be crucial to the prevention and treatment of these illnesses. Altogether, this project will provide insight as to whether there exists a long-term impact of cannabis exposure during development to substantiate a neurobiological "gateway" hypothesis and, if so, help to identify potential risk factors in adolescence that influence the vulnerability for drug abuse in adulthood.