Insulin signaling, dopamine sensitization and cocaine cue-induced relapse

描述(由申请人提供)：尽管有证据表明“中脑边缘多巴胺敏化”与长期戒断可卡因期间对奖赏线索的高敏感性有关，但这种现象背后的分子机制却知之甚少。在这里，我们测试了一个新的假设，即反复暴露可卡因导致多巴胺神经元内能量利用的变化会导致胰岛素信号的中断，从而通过多巴胺转运体(DAT)对突触的多巴胺清除产生负面影响。然后，这会导致多巴胺对可卡因配对线索的反应增加，从而导致寻找可卡因的行为。与可卡因使用相关的饮食变化对这些过程的协同影响将使用高果糖饮食来评估，我们之前已经证明高果糖饮食会扰乱大脑中的胰岛素信号。线粒体功能和胰岛素信号的标记物将在腹侧被盖区多巴胺神经元中进行评估，死后收集的可卡因自我注射不同时间后戒断，在有或没有获得高果糖饮食的情况下收集。在平行研究中，将通过快速扫描循环伏安法评估这种暴露对多巴胺清除的影响，同时监测与可卡因配对的线索对可卡因寻找行为的影响。最后，将通过用吡格列酮阻断胰岛素抵抗的发展来评估胰岛素信号失调与这些神经化学和行为现象之间的因果联系。吡格列酮是一种目前被批准用于治疗2型糖尿病的药物。这些研究将提供有关可卡因诱导的代谢异常在降低复发门槛方面的作用的基本信息，并可能发现治疗干预的新靶点。

DESCRIPTION (provided by applicant): Despite evidence linking "mesolimbic dopamine sensitization" to hypersensitivity to reward-paired cues during protracted cocaine withdrawal; the molecular mechanisms underlying this phenomenon are poorly understood. Here, we test the novel hypothesis that changes in energy utilization within dopamine neurons brought about by repeated cocaine exposure result in disruption of insulin signaling, which negatively impacts synaptic dopamine clearance via the dopamine transporter (DAT). This then results in heightened dopamine transmission in response to cocaine-paired cues, thereby precipitating cocaine-seeking behaviors. The synergistic influence of dietary changes associated with cocaine use on these processes will be assessed using a high-fructose diet that we have previously shown to disrupt insulin signaling in the brain. Markers of mitochondrial function and insulin signaling will be assessed in ventral tegmental area dopamine neurons, post-mortem, collected after varying durations of cocaine self-administration followed by withdrawal, with and without access to a high-fructose diet. In parallel studies, the impact of such exposures on dopamine clearance will be assessed by fast-scan-cyclic voltammetry while monitoring the impact of cocaine-paired cues on cocaine seeking actions. Finally, a causal link between insulin signaling dysregulation and these neurochemical and behavioral phenomena will be assessed by blocking development of insulin resistance with pioglitazone, a drug currently approved for the treatment of Type 2 diabetes. These studies will provide fundamental information regarding the role of cocaine-induced metabolic aberrations in lowering the threshold for relapse and may uncover new targets for therapeutic intervention.