Defining the descending pain modulatory circuit

项目摘要 中枢神经系统有一个内在的疼痛调节系统，调节伤害性处理 从脑干向下投射到脊髓背角。腹外侧 中脑导水管周围灰质（periaqueductal gray，vlPAG）整合感觉信息与来自高级皮质和皮质下的输入 区域，并将投射发送到延髓头端腹内侧（RVM），这些投射被中继到脊髓背角。 脊髓vlPAG和RVM两者在参与多个行为方面是异质的。 电路.拟议的研究建立在Heinricher实验室以前广泛的工作基础上， 来自RVM的输出，显示来自该区域的双向疼痛控制由两个 生理上定义的细胞类别，“ON-细胞”和“OFF-细胞”，其分别促进和抑制背侧肌的运动。 不同条件下的角伤害性传递。英格拉姆实验室拥有研究阿片类药物的专业知识 PAG和RVM内的作用，以及持续炎症的两个区域的适应。提出 病毒光遗传学策略将绘制和定义调节参与免疫调节的RVM ON细胞的vlPAG回路。 促进疼痛和阐明潜在的细胞机制，改变RVM输出的平衡， 疼痛抑制到疼痛促进，伴有持续性炎症。两人的专业知识结合在一起 实验室将专注于使用RVM末端的光遗传学刺激鉴定PAG-RVM突触 来自PAG。体外脑切片记录（Ingram实验室）将检查PAG的异质性 输出到RVM和PAG-RVM突触，以及突触可塑性的细胞机制，诱导 持续性炎症这些研究将使用μ-阿片受体的荧光标记来区分 假定ON细胞来自切片中的其他类别，以确定PAG终末是否直接突触 ON细胞，OFF细胞，或两者兼而有之，以及释放的神经递质。体内单细胞记录 研究（Heinricher实验室）将确定炎症诱导的PAG-RVM突触变化如何控制 RVM神经元的特定群体的兴奋性，并建立这些变化和疼痛之间的联系 行为。更好地理解疼痛的分子、细胞和电路水平机制是 如果我们想开发更好的治疗方法，通过仔细绘制从PAG到 持续性炎症发展期间的RVM，并通过将这些与定义的RVM输出联系起来， 行为，我们可以开始确定在这个复杂的网络中的相互作用，并获得新的见解如何 疼痛调节系统在急性和慢性疼痛中被募集和调节。

PROJECT SUMMARY The central nervous system has an intrinsic pain modulatory system that regulates nociceptive processing through descending projections from the brainstem to the spinal cord dorsal horn. The ventrolateral periaqueductal gray (vlPAG) integrates sensory information with input from higher cortical and subcortical areas, and sends projections to the rostral ventromedial medulla (RVM) that are relayed to the dorsal horn of the spinal cord. Both the vlPAG and RVM are heterogenous with respect to participating in multiple behavioral circuits. The proposed studies build on extensive previous work from the Heinricher laboratory that has defined the output from the RVM, showing that bidirectional pain control from this region is mediated by two physiologically defined cell classes, “ON-cells” and “OFF-cells,” that respectively facilitate and inhibit dorsal horn nociceptive transmission under different conditions. The Ingram laboratory has expertise studying opioid actions within the PAG and RVM, as well as adaptations in both areas with persistent inflammation. Proposed viral optogenetic strategies will map and define the vlPAG circuit that regulates RVM ON-cells involved in the facilitation of pain and elucidate underlying cellular mechanisms that shift the balance of RVM output from inhibition of pain to facilitation of pain with persistent inflammation. The combined expertise of the two laboratories will focus on identified PAG-RVM synapses using optogenetic stimulation of RVM terminals originating from the PAG. In vitro brain-slice recordings (Ingram lab) will examine the heterogeneity of PAG output to the RVM and PAG-RVM synapses, as well as cellular mechanisms of synaptic plasticity induced in persistent inflammation. These studies will use a fluorescent label for the μ-opioid receptor to differentiate presumed ON-cells from other classes in the slice to determine whether PAG terminals directly synapse on ON-cells, OFF-cells, or both, as well as what neurotransmitters are released. In vivo single-cell recording studies (Heinricher lab) will determine how inflammation-induced changes in PAG-RVM synapses control excitability of specific populations of RVM neurons and establish the link between these changes and pain behaviors. A better understanding of molecular, cellular, and circuit-level mechanisms that underlie pain is essential if we are to develop better treatments. By carefully mapping the descending projections from PAG to RVM during the development of persistent inflammation, and by tying these to defined RVM outputs and behavior, we can begin to determine the interactions in this complex network, and gain new insights into how pain-modulating systems are recruited and modulated in acute and chronic pain.