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

描述（由申请人提供）：药物成瘾是一种严重和多产的精神疾病，涉及持续复发，尽管真诚的努力，以避免。这项研究研究的神经生物学机制，增加了长期禁欲后复发的倾向，以确定潜在的治疗干预，以促进禁欲的新目标。先前的研究表明，μ阿片受体刺激的核（NAc）不发挥作用，在可卡因寻求行为使用啮齿动物模型的可卡因复吸。然而，我们发现，NAc注入内源性阿片β-内啡肽将主要通过激活NAc中的μ阿片受体（MOR 1）来触发可卡因寻求。重要的是，我们发现，从早期到晚期可卡因戒断，NAc中的MOR 1表达逐渐增加，与可卡因寻求行为的时间依赖性增加（孵育）一致。此外，我们的初步数据表明，NAc中MOR 1表达的增加与下丘脑弓状核（Arc）中β-内啡肽前体阿黑皮素原（POMC）表达的增加有关。这项研究的目的是研究这些内源性阿片系统中神经适应的功能对长期可卡因戒断后复发倾向增加的贡献。目的I中的研究将确定NAc中MOR 1刺激在早期和晚期从慢性可卡因自我给药中戒断后触发复发行为的能力。将测试β-内啡肽和MOR 1激动剂DAMGO的NAc内输注在实验的消退和恢复阶段增加复发行为的能力。类似的DAMGO的NAc内输注将用于评估体内MOR 1信号传导，作为与行为实验平行的生物化学。Aim II的研究将使用原位杂交来测量Arc中的POMC表达，并在早期和晚期停药后使用凝胶蛋白质印迹法来测量Arc和NAc中的β-内啡肽水平。通过在消退/恢复试验中用抗β-内啡肽和MOR 1拮抗剂CTAP中和NAc中的内源性β-内啡肽释放，研究POMC表达和β-内啡肽合成增加对复发倾向的贡献。压力情境激活了Arc中的POMC神经元，并触发可卡因寻求行为，但POMC神经元在复发行为中的作用尚未研究。目的III中的研究将使用光遗传学方法结合在POMC启动子控制下表达Cre重组酶的小鼠中诱导型病毒载体介导的通道视紫红质-2表达来研究POMC Arc神经元的选择性激活对早期和晚期戒断中可卡因寻求的影响。NAc中β-内啡肽释放在由POMC神经元激活诱导的复发中的作用将通过NAc内输注抗β-内啡肽来评估。总之，这些研究将确定内源性μ阿片受体系统中持续的神经适应在长期戒断可卡因复发倾向增加中的作用。

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.