Defining the descending pain modulatory circuit

项目总结 中枢神经系统有一个内在的痛觉调节系统，它调节伤害性信息的处理。 通过从脑干到脊髓背角的下行投射。腹外侧核 中脑导水管周围灰质(VlPAG)将感觉信息与高级皮质和皮质下的输入整合在一起 向延髓头端腹内侧(RVM)发出投射，并将其传递到延髓背角。 脊髓。VlPAG和RVM在参与多个行为方面都是异质的 电路。拟议的研究建立在Heinricher实验室之前广泛的工作基础上，该实验室已经定义了 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型，“开细胞”和“离细胞”，分别促进和抑制背部 角在不同条件下的伤害性传递。英格拉姆实验室拥有研究阿片类药物的专业知识 在PAG和RVM内的作用，以及在这两个区域的适应与持续的炎症。建议 病毒光遗传策略将映射和定义vlPAG电路，该电路调节RVM ON-参与 促进疼痛，并阐明改变RVM输出平衡的潜在细胞机制 抑制疼痛到促进持续炎症的疼痛。两者的专业知识结合在一起 实验室将专注于利用RVM终末的光遗传刺激来识别PAG-RVM突触 发源于PAG。体外脑片记录(英格拉姆实验室)将检查PAG的异质性 向RVM和PAG-RVM突触的输出，以及诱导突触可塑性的细胞机制 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 推测为ON-来自脑片中其他类别的细胞，以确定PAG终末是否直接突触 开细胞、离细胞或两者兼而有之，以及释放的神经递质。活体单细胞记录 研究(Heinricher实验室)将确定炎症诱导的PAG-RVM突触的变化如何控制 RVM神经元特定群体的兴奋性并建立这些变化与疼痛之间的联系 行为。更好地理解疼痛背后的分子、细胞和电路水平的机制是 如果我们要开发更好的治疗方法，这是必不可少的。通过仔细地将PAG的下降投影映射到 在持续性炎症发展过程中的RVM，并通过将这些与定义的RVM输出和 行为，我们就可以开始确定这个复杂网络中的相互作用，并对如何 疼痛调节系统在急性和慢性疼痛中被招募和调节。

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.