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

描述(申请人提供)：吸毒成瘾是一种严重和多发的精神疾病，尽管真诚地努力戒除，但仍会持续复发。这项研究研究了在长期戒断后增加复发倾向的神经生物学机制，以确定潜在的治疗干预的新靶点，以促进戒酒。先前的研究表明，在可卡因复吸的啮齿动物模型中，伏隔核(NAC)中的Mu阿片受体刺激在寻找可卡因的行为中没有发挥作用。然而，我们发现，NAC注入内源性阿片剂β-内啡肽将主要通过激活NAC中的MU阿片受体(MOR1)来触发可卡因寻找。重要的是，我们发现，从可卡因戒断的早期到晚期，NAC中MOR1的表达逐渐增加，这与可卡因寻找行为的时间依赖增加(潜伏期)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-内啡肽前体阿片黑素皮质素(POMC)表达的增加平行。这项拟议研究的目的是研究这些内源性阿片系统中的神经适应对长期戒断可卡因复发倾向增加的功能贡献。AIM I的研究将确定刺激NAC中的MOR1在早期和晚期戒断慢性可卡因自我给药后触发复发行为的能力。NAC内注射β-内啡肽和MOR1激动剂DAMGO将测试它们在实验的消退和恢复阶段增加复发行为的能力。类似的NAC内注射DAMGO将被用来评估体内的MOR1信号，作为与行为实验平行的生化实验。AIM II的研究将使用原位杂交来测量POMC在Arc中的表达，以及在早期和晚期戒断时间后，在Arc和Nac中的β-内啡肽水平的凝胶Western Blot。POMC表达增加和β-内啡肽合成增加对复发倾向的贡献将通过在消退/恢复试验中用抗β-内啡肽和MOR1拮抗剂CTAP中和NAC中的内源性β-内啡肽释放来研究。应激状态激活了Arc中的POMC神经元，并触发了可卡因寻找行为，但POMC神经元在复吸行为中的作用尚未被研究。AIM III的研究将使用一种光遗传学方法，结合可诱导的病毒载体介导的通道视紫红质-2表达的光遗传学方法，在POMC启动子控制下表达Cre重组酶的小鼠中，研究POMC Arc神经元的选择性激活对戒断早期和晚期寻求可卡因的影响。NAC中的β-内啡肽释放在POMC神经元激活引起的复发中的作用将通过在NAC内注射抗β-内啡肽来评估。总而言之，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.