Role of Endogenous Opiate Systems in Cocaine Relapse after Long-Term Abstinence

描述（由申请人提供）：吸毒成瘾是一种严重和多产的精神疾病，尽管有真诚的努力戒除，但仍会持续复发。本研究研究了长期戒断后复发倾向增加的神经生物学机制，以确定促进戒断的潜在治疗干预的新靶点。先前的研究表明，在可卡因复发的啮齿动物模型中，伏隔核（NAc）的mu阿片受体刺激在可卡因寻求行为中不起作用。然而，我们发现内源性阿片β -内啡肽的NAc输注将主要通过激活NAc中的mu阿片受体（MOR1）来触发可卡因寻求。重要的是，我们发现，从可卡因戒断早期到晚期，NAc中MOR1的表达逐渐增加，与可卡因寻求行为的时间依赖性增加（潜伏期）相一致。此外，我们的初步数据表明，NAc中MOR1表达的增加与下丘脑弓状核（Arc）中β -内啡肽前体proopiomelanocortin （POMC）表达的增加是平行的。拟议研究的目的是研究这些内源性阿片系统的神经适应性在长期可卡因戒断中增加复发倾向的功能贡献。Aim I的研究将确定NAc中MOR1刺激引发慢性可卡因自我给药早期和晚期戒断后复发行为的能力。nac内输注β -内啡肽和MOR1激动剂DAMGO将在实验的消退和恢复阶段测试它们增加复发行为的能力。类似的nac内注射DAMGO将用于评估体内MOR1信号，作为与行为实验平行的生化实验。Aim II的研究将在早期和晚期停药后使用原位杂交技术测量Arc中的POMC表达，并使用in Gel Western Blot检测Arc和NAc中的β -内啡肽水平。POMC表达和β -内啡肽合成增加对复发倾向的贡献将通过在消退/恢复试验中使用抗β -内啡肽和MOR1拮抗剂CTAP中和NAc中内源性β -内啡肽释放来研究。应激情境激活Arc中的POMC神经元，并引发可卡因寻求行为，但POMC神经元在复发行为中的作用尚未得到研究。Aim III的研究将利用光遗传学方法结合诱导病毒载体介导的通道-视紫红质-2表达，在POMC启动子控制下表达Cre重组酶的小鼠中，研究POMC Arc神经元选择性激活对早期和晚期戒断可卡因寻求的影响。在POMC神经元激活引起的复发中，β -内啡肽释放在NAc中的作用将通过NAc内注射抗β -内啡肽来评估。总之，这些研究将确定内源性mu阿片受体系统中持续的神经适应在长期戒断中增加可卡因复发倾向中的作用。

DESCRIPTION (provided by applicant): Drug addiction is a serious and prolific mental illness involving persistent relapse despite sincere efforts to abstain. This research studies the neurobiological mechanisms that increase the propensity for relapse after prolonged abstinence to determine novel targets for potential therapeutic intervention to promote abstinence. Previous studies suggest that mu opiate receptor stimulation in the nucleus accumbens (NAc) does not play a role in cocaine-seeking behavior using rodent models of cocaine relapse. However, we found that NAc infusions of the endogenous opiate beta-endorphinwill trigger cocaine seeking primarily via activation of mu opiate receptors (MOR1) in the NAc. Importantly, we found that MOR1 expression in the NAc progressively increases from early to late cocaine withdrawal, coinciding with time-dependent increases (incubation) in cocaine-seeking behavior. Moreover, our preliminary data suggest that increases in MOR1 expression in the NAc are paralleled by increased expression of the beta-endorphinprecursor proopiomelanocortin (POMC) in the arcuate nucleus of the hypothalamus (Arc). The goal of the proposed research is to study the functional contribution of neuroadaptations in these endogenous opiate systems to the increased propensity for relapse in long-term cocaine withdrawal. Studies in Aim I will determine the ability of MOR1 stimulation in the NAc to trigger relapse behavior after early and late withdrawal from chronic cocaine self-administration. Intra-NAc infusions of beta-endorphinand the MOR1 agonist DAMGO will be tested for their ability to increase relapse behavior in both extinction and reinstatement phases of experimentation. Similar intra-NAc infusions of DAMGO will be used to assess MOR1 signaling in vivo as a biochemical parallel to behavioral experiments. Studies in Aim II will use in situ hybridization to measure POMC expression in the Arc, and In Gel Western Blot of beta-endorphinlevels in the Arc and NAc, after both early and late withdrawal times. The contribution of increased POMC expression and beta-endorphin synthesis to the propensity for relapse will be studied by neutralizing endogenous beta-endorphinrelease in the NAc with anti-beta-endorphin and the MOR1 antagonist CTAP in extinction/reinstatement tests. Stressful situations activate POMC neurons in the Arc, and trigger cocaine-seeking behavior, but the role of POMC neurons in relapse behavior has not been studied. Studies in Aim III will investigate the effects of selective activation of POMC Arc neurons on cocaine seeking in early and late withdrawal using an optogenetic approach combining inducible viral vector-mediated channel-rhodopsin-2 expression in mice expressing Cre recombinase under POMC promoter control. The role of beta-endorphinrelease in the NAc in relapse induced by activation of POMC neurons will be assessed with intra-NAc infusions of anti-beta-endorphin. Together, these studies will determine the role of persistent neuroadaptations in endogenous mu opiate receptor systems in the increased propensity for cocaine relapse in prolonged abstinence.