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

描述(申请人提供)：大麻是青少年最常使用的非法药物，在使用“重度”药物和精神疾病之前，接触大麻通常是最常见的。这些数据似乎支持有争议的“门户”假说，即大麻是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春期使用大麻与后来的药物滥用之间存在联系，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相关性。可复制的动物数据表明，青春期接触大麻会增强成年海洛因的自我给药行为，并导致伏隔核(ACB)中前脑啡肽原(Penk)的离散变化，前脑啡肽原(Penk)是一种对奖赏和享乐状态至关重要的基因，伏隔核是大脑中与奖赏相关的区域。拟议的工作将直接测试早发性大麻使用引起的Penk障碍与逐渐使用其他非法药物之间是否存在因果联系。病毒介导的基因转移(Penk过表达)和RNA干扰(Penk基因敲除)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将确定直接操纵ACB外壳中的Penk基因是否会改变海洛因的自我给药行为。通过使用体内微透析研究Penk的遗传操作是否改变了阿片剂诱导的ACB壳中的多巴胺水平，将确定与奖励相关的大脑区域的神经递质紊乱(特定目标2)。为了表征可能导致与Penk基因操作相关的行为和神经化学差异的特定分子变化，将分析大脑与阿片、多巴能和大麻类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，了解易患药物滥用障碍的危险因素对预防和治疗这些疾病至关重要。总之，该项目将深入了解在发育过程中是否存在大麻暴露的长期影响，以证实神经生物学“门户”假说，如果存在，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.