Descending facilitation of pain by mu-opioid receptor-expressing neurons in the rostral ventromedial medulla

项目总结/摘要 疼痛是一种使人衰弱的普遍疾病，严重影响生活质量。不幸的是，我们目前 治疗选择受到副作用的限制，并且调节疼痛信号传导的途径并不完全 明白延髓头端腹内侧区（RVM）是脑干的一个部位，在疼痛中起着关键作用 调制，主要是通过发送下行投射到脊髓。虽然非特定的电气 刺激RVM产生镇痛，RVM神经元可以促进或抑制疼痛。RVM脊柱 投射可以基于它们对以下的响应被表征为ON-细胞、OFF-细胞或NEUTRAL-细胞， 对疼痛反应的影响，但许多细节仍不清楚。吗啡作用于μ阿片受体（莫尔） 抑制神经元活性，并部分通过激活OFF-细胞和抑制ON-细胞产生镇痛作用。因此，在本发明中， 因此ON-细胞表达莫尔。许多研究支持这一论断，即细胞上的电路是牵连 慢性疼痛和阿片类药物引起的痛觉过敏。然而，直到最近，我们还缺乏必要的遗传工具， 解剖RVM中表达MOR的神经元（包括ON细胞）的回路。随着最近的事态发展 在Oprm 1-Cre基因敲入小鼠中，我们现在有了更详细地研究这些电路所必需的遗传工具。 因此，本提案的目的是检验以下假设：莫尔+ RVM神经元通过抑制 背角浅层的中间神经元。我将结合基因，分子， 电生理学和行为学方法。目的1将研究RVM中哪些细胞类型表达 通过病毒追踪、荧光原位杂交（FISH）和免疫组织化学（IHC）检测莫尔。目标2A将 通过光遗传学和切片鉴定背角中间神经元接受的莫尔+ RVM输入 电生理学目的2B将探讨电生理，神经化学，和形态表型， 背角中间神经元使用组合的电生理学从莫尔+ RVM神经元接收输入， 解剖学方法目标3将检验莫尔+右心室肌神经元促进机械、化学、 和热痛通过使用化学遗传学和行为测定的急性和慢性神经病变 痛苦本建议书中详细介绍的工作至关重要，因为要加深对电路的理解， 作为RVM的基础，可以为新型疼痛疗法的发展铺平道路，并将推动该领域的发展。 神经科学 此外，这个提议的灵感来自于我对麻醉学的临床兴趣，我计划在那里工作， 疼痛专家和研究疼痛信号机制，以尽量减少患者的痛苦和提高质量 生活专业，技术和智力技能，将在本奖学金的过程中发展 将使我成为一名成功的麻醉学学术科学家。

Project Summary/Abstract Pain is a debilitating and prevalent condition which severely impacts quality of life. Unfortunately, our current treatment options are limited by adverse effects, and the pathways modulating pain signaling are not fully understood. The rostral ventromedial medulla (RVM) is a brainstem site which plays a critical role in pain modulation, primarily by sending descending projections to the spinal cord. While non-specific electrical stimulation of the RVM produces analgesia, RVM neurons can either facilitate or inhibit pain. RVM spinal projections can be characterized as ON-cells, OFF-cells, or NEUTRAL-cells based on their response to, and effect on, nocifensive reflexes, but many details remain unclear. Morphine acts at the mu-opioid receptor (MOR) to inhibit neuronal activity and produces analgesia in part by activating OFF-cells and inhibiting ON-cells. Thus, it follows that ON-cells express MOR. Numerous studies support the assertion that ON-cell circuitry is implicated in chronic pain and opioid-induced hyperalgesia. However, until recently we lacked the genetic tools necessary to dissect the circuitry of MOR-expressing neurons, including ON-cells, in the RVM. With the recent development of the Oprm1-Cre knock-in mouse, we now have the genetic tool necessary to study these circuits in better detail. The goal of this proposal is to therefore test the hypothesis that MOR+ RVM neurons facilitate pain by inhibiting interneurons in the superficial dorsal horn. I will test this hypothesis using a combination of genetic, molecular, electrophysiological, and behavioral approaches. Aim 1 will investigate which cell types in the RVM express MOR through viral tracing, fluorescent in situ hybridization (FISH), and immunohistochemistry (IHC). Aim 2A will identify the MOR+ RVM inputs received by interneurons in the dorsal horn through optogenetics and slice electrophysiology. Aim 2B will explore the electrophysiological, neurochemical, and morphological phenotype of dorsal horn interneurons receiving input from MOR+ RVM neurons using a combined electrophysiology and anatomical approach. Aim 3 will test the hypothesis that MOR+ RVM neurons facilitate mechanical, chemical, and thermal pain through the use of chemogenetics and behavioral assays of acute and chronic neuropathic pain. The work detailed in this proposal is critically important because an enhanced understanding of the circuitry underlying the RVM can pave the way for the development of novel pain therapeutics and will advance the field of neuroscience. Furthermore, this proposal is heavily inspired by my clinical interest in anesthesiology, where I plan to work as a pain specialist and investigate pain signaling mechanisms to minimize patient suffering and improve quality of life. The professional, technical, and intellectual skills which will be developed over the course of this fellowship will position me for success as a physician-scientist in academic anesthesiology.