Novel Circuits and Mechanisms of Descending Pain Modulation

项目摘要/摘要 慢性疼痛困扰着数百万患者，然而治疗在很大程度上是无效的，新的、有针对性的发展 治疗受到疼痛神经生物学知识差距的限制。尽管最近取得了进展，但关键问题 关于上行和下行神经令人难以置信的复杂细胞和功能组织 控制疼痛处理的电路。回答这些问题对于开发新的、更多的 治疗急性和慢性疼痛的有效和更有针对性的疗法。这项建议的主要目的是 识别我们最近发现的一组新神经元的电路连接和突触机制 在侧脑桥。位于A5去甲肾上腺素能细胞群旁边的这些神经元(我们称之为LJA5) 表达前强啡肽和谷氨酸脱羧酶1(GAD1)。它们不同于A5去甲肾上腺素 神经元不表达酪氨酸羟化酶。LJA5神经元投射到脊髓I层的所有水平 前臂旁核(PB)和中脑导水管周围灰质(PAG)。值得注意的是，我们 表明这些神经元在痛觉调节中起着重要作用。具体地说，化学生成激活 LJA5神经元抑制辣椒素和炎症诱导的机械性疼痛，但不能抑制热敏感性， 而LJA5的化学生成抑制增强了炎症过程中的机械超敏反应。我们的 初步数据还显示，LJA5神经元的化学生成激活强烈地减轻了神经病变 通过全身给药和鞘内给药来缓解疼痛。总而言之，这些发现表明 LJA5神经元及其投射是下行痛觉调制的新成分，也是姿势 关于这个新电路有许多重要的问题：1)LJA5神经元调节哪些类型的疼痛？2) LJA5神经元的主要投射/输出是什么？3)LJA5利用什么突触机制 神经元？我们的中心假设是LJA5神经元通过控制突触来调节疼痛的处理 脊髓背角I层的传递。我们将通过以下三个具体目标来检验这一假设 使用包括化学遗传操作和行为测试在内的多学科方法， 膜片钳记录在创新的完整脊髓准备和轴突双光子钙离子成像中的应用 主要传入中央终末。目的1将建立LJA5神经元在小鼠模型中的作用 炎症性和神经性疼痛。目标2将研究主要LJA5投影的功能意义。目标 3将确定介导脊髓中LJA5神经元抗伤害感受效应的突触机制 电源线。这一提议将定义与疼痛有关的一种新的下行通路的基本特征 调制，包括其功能连接、突触机制及其在急、慢性疼痛中的作用 各州。这项工作具有变革性，因为它确定了一种新的球脊髓痛觉调制途径，即 在我们对疼痛的基本理解方面取得了重大进展，这可能会为疼痛控制提供替代方法。

Project Summary/Abstract Chronic pain afflicts millions of patients, yet treatments are largely ineffective, and development of new, targeted therapies is limited by knowledge gaps in the neurobiology of pain. Despite recent progress, key questions remain about the incredibly complex cellular and functional organization of ascending and descending neural circuits that control pain processing. Answering these questions is essential for developing new, more efficacious, and better targeted therapeutics for acute and chronic pain. The main objective of this proposal is to identify the circuit connections and synaptic mechanisms of a novel group of neurons that we recently discovered in the lateral pons. Situated juxta the A5 noradrenergic cell group, these neurons (which we termed LJA5) express prodynorphin and glutamic acid decarboxylase 1 (GAD1). They are distinct from the A5 noradrenergic neurons as they do not express tyrosine hydroxylase. LJA5 neurons project to all spinal levels of lamina I of the dorsal horn (DH), as well as to the parabrachial nucleus (PB) and the periaqueductal gray (PAG). Notably, we showed that these neurons play an important role in pain regulation. Specifically, chemogenetic activation of LJA5 neurons suppressed capsaicin- and inflammation-induced mechanical pain, but not thermal sensitivity, whereas chemogenetic inhibition of LJA5 enhanced mechanical hypersensitivity during inflammation. Our preliminary data also showed that chemogenetic activation of LJA5 neurons strongly attenuated neuropathic pain both via systemic and intrathecal administration of a designer drug. Collectively, these findings suggest that LJA5 neurons and their projections represent a novel component of descending pain modulation, and also pose many important questions about this novel circuit: 1) Which types of pain are regulated by LJA5 neurons? 2) What are the key projections/outputs of LJA5 neurons? 3) What synaptic mechanisms are utilized by LJA5 neurons? Our central hypothesis is that LJA5 neurons modulate pain processing by controlling synaptic transmission in lamina I of the dorsal horn of the spinal cord. We will test this hypothesis in 3 specific aims by using a multidisciplinary approach that includes chemogenetic manipulation combined with behavioral testing, patch-clamp recording in innovative intact spinal cord preparation and 2-photon Ca2+ imaging in axonal boutons of primary afferent central terminals. Aim 1 will establish the role of LJA5 neurons in mouse models of inflammatory and neuropathic pain. Aim 2 will examine functional significance of the main LJA5 projections. Aim 3 will determine synaptic mechanisms that mediate the antinociceptive effects of LJA5 neurons in the spinal cord. This proposal will define fundamental characteristics of a novel descending pathway involved in pain modulation, including its functional connectivity, synaptic mechanisms and its role in acute and chronic pain states. This work is transformative because it identifies a novel bulbospinal pain modulatory pathway, a significant advance in our basic understanding of pain that may offer alternative approaches to pain control.