Circuit mechanisms for opioid analgesia and addiction in prefrontal cortex

项目摘要(摘要) MU阿片受体(MOR)在神经系统中广泛表达，并在两种止痛药中起调节作用 以及阿片类药物的成瘾效应。尽管美国目前存在阿片类药物危机，但阿片类药物提供了 无与伦比的止痛功效，适用于各种疼痛情况。解离阿片类止痛药 和成瘾效应，至关重要的是确定哪些神经回路和细胞类型分别调节这些 效果。由于内侧前额叶皮质(MPFC)的功能，MOR信号具有特殊的意义 作为上行和下行痛环的关键整合节点及其与皮质下的强连接 奖励电路。然而，阿片类药物最终如何改变谷氨酸能mPFC输出神经元的活性 对阿片成瘾和疼痛行为的调节尚不清楚。皮层的主要输出包括两个截然不同的 第5层谷氨酸能投射神经元的群体：脑内(IT)和锥体束(PT)神经元。 IT神经元主要投射到皮质内和纹状体，而PT神经元则广泛投射和稳定。 直接调节整个大脑的神经活动。尽管有证据支持莫尔依赖于 在疼痛和成瘾中，初步数据表明，MOR不直接在IT或PT细胞上表达。 该项目旨在(1)确定阿片类药物暴露对小鼠mPFC、IT和PT细胞活性的影响；(2) 阐明mPFC、IT和PT细胞在阿片成瘾和镇痛中的作用。为了确定如何 阿片类药物调节IT和PT细胞的活动，双色钙成像将被用作神经元活动的替代。 每个人群的神经动力学特征将在基线、急性和慢性吗啡期间进行表征 通过皮下植入泵暴露，以及在纳洛酮催促戒断期间。评估 IT和PT细胞对阿片成瘾、mPFC IT或PT细胞活性的贡献将是化学发生的 抑制成瘾模型包括吗啡条件性位置偏爱和羟考酮自身 行政管理。最后，IT和PT细胞在吗啡镇痛和阿片类药物诱导的耐受中的作用 而痛觉过敏将通过急性和慢性疼痛后对mPFC IT或PT细胞的化学生成抑制来评估。 慢性吗啡暴露对热痛(热痛)和机械痛(冯-弗雷)的影响。这个项目将 建立阿片类药物成瘾和止痛作用分离的基础知识， 照亮非成瘾性疼痛治疗的靶点。 通过这项研究提案和相关的培训计划，我将获得出色的神经解剖学培训， 诺斯大学支持性训练环境中的成瘾和疼痛行为以及神经动力学 卡罗莱纳州医学博士项目。这次培训将为我提供必要的技术和专业技能 成为学术医学中心的领导者，追求我实践止痛药和 作为一名内科科学家，研究疼痛的创新非成瘾疗法。

PROJECT SUMMARY (ABSTRACT) The mu opioid receptor (MOR) is widely expressed throughout the nervous system and mediates both analgesic and addictive effects of opioids. Despite the current opioid crisis in the United States, opioid drugs offer unparalleled analgesic efficacy and are prescribed for a variety of pain conditions. To dissociate opioid analgesic and addictive effects, it is essential to determine which neural circuits and cell types mediate each of these effects. MOR signaling in medial prefrontal cortex (mPFC) is of particular significance due to the mPFC function as a key integrative node in ascending and descending pain circuits and its strong connectivity to subcortical reward circuitry. However, how opioids eventually alter the activity of glutamatergic mPFC output neurons to modulate opioid addiction and pain behaviors is unknown. The main outputs of the cortex include two distinct populations of layer 5 glutamatergic projection neurons: intratelencephalic (IT) and pyramidal tract (PT) neurons. IT neurons predominantly project intracortically and to striatum, while PT neurons project broadly and are poised to directly modulate neural activity throughout the brain. Despite evidence supporting a MOR-dependent role for mPFC in pain and addiction, preliminary data suggest that MOR is not expressed directly on IT or PT cells. This project aims to (1) determine how opioid exposure impacts mPFC IT and PT cell activity in mice and (2) delineate the contribution of mPFC IT and PT cells to opioid addiction and analgesia. In order to determine how opioids modulate IT and PT cell activity, dual-color calcium imaging will be used as a proxy for neuronal activity. Neural dynamics of each population will be characterized at baseline, during acute and chronic morphine exposure through subcutaneously implanted pumps, and during naloxone-precipitated withdrawal. To assess the contribution of IT and PT cells to opioid addiction, mPFC IT or PT cell activity will be chemogenetically suppressed in addiction models including morphine conditioned place preference and oxycodone self- administration. Finally, the contribution of IT and PT cells to morphine analgesia and opioid-induced tolerance and hyperalgesia will be assessed through chemogenetic suppression of mPFC IT or PT cells after acute and chronic morphine exposure in assays for thermal (hotplate) and mechanical (von Frey) pain. This project will establish foundational knowledge in the dissociation of the addictive and analgesic effects of opioids, illuminating targets for nonaddictive pain therapies. Through this research proposal and associated training plan, I will gain excellent training in neuroanatomy, addiction and pain behaviors, and neural dynamics in a supportive training environment at the University of North Carolina MD/PhD Program. This training will provide me with the technical and professional skills necessary to become a leader at an academic medical center and pursue my goals of practicing pain medicine and researching innovative non-addictive therapies for pain as a physician-scientist.