Vagal nociceptive pathway mediating pain from the esophagus

胃灼热是胃食管反流病（GERD）的主要症状，约550万例 办公室访问/年，其负担在美国> 90亿美元/年。虽然在大多数GERD患者中， 抑酸是一种有效的治疗这种疼痛，在充分20-30%的患者的胃灼热没有缓解;这些 人们经常求助于中枢作用药物来缓解。我们的长期目标是填补一个主要的空白， 的传入途径介导胃灼热，使新的战略，以减轻酸抑制抗性 痛苦我们将讨论我们的新假设，即胃灼热是由一个相对未经研究的伤害感受器介导的 亚型，即迷走神经颈静脉传入C纤维。我们的假设基于两个前提：首先， 两种可区分但重叠的人类食管疼痛感觉：胃灼热， 可靠地由食管酸注入诱发，和食管疼痛（更类似于其他类型的内脏疼痛）， 这是由食管扩张引起的。同时，有两种亚型的食管C- 纤维伤害感受器（迷走神经颈静脉和脊髓背根神经节），具有有利于优先检测酸的传入特性 （支配粘膜的迷走神经颈静脉伤害感受器）和机械扩张（扩张敏感性DRG） 伤害感受器）。在目标1（发现新靶点）中，我们将确定哪种迷走传入神经亚型具有 食管粘膜中的外周神经末梢，使得其可能暴露于管腔酸， 由酸激活，并在脑干区域有中枢终末，涉及内脏伤害性知觉 刺激。迷走食管传入神经可分为4个主要亚型：P2 X2 +/TRPV 1-结状神经 机械感受器，P2 X2 +/TRPV 1+结状C纤维酸-，Tac 1 +/TRPV 1+颈静脉伤害性感受器， 特征辣椒素不敏感的颈静脉纤维Tac 1 +/TRPV 1-。我们开发了创新的方法， 选择性表达这些亚型中的报告基因，包括与P2 X2-Cre或Tac 1-Cre杂交的TRPV 1-Flp， 获得的小鼠，其中结瘤或颈静脉亚型可以通过适当的双重Flp-/Cre-选择性靶向， 敏感的AAV载体。在目标2（验证新靶点）中，我们将开始评估选择性激活的作用 仅迷走神经颈静脉C-纤维（Tac 1 +/TRPV 1+亚型）在食管中引发疼痛感觉 通过在食管颈静脉C-纤维中选择性表达DREADD受体hM 3Dq的小鼠和大鼠 (Tac1+/TRPV 1+）神经元的疼痛反应，并评估对hM 3Dq全身给药的疼痛诱导反应 激动剂N -氧化氯氮平（CNO）。

Heartburn is the main symptom of gastroesophageal reflux disease (GERD) which accounts for > 5.5 million office visits/year and its burden is >$9 billion/year in the United States. While in a majority of GERD patients, acid suppression is an effective therapy for this pain, in fully 20-30% of patients’ heartburn is not relieved; these people often resort to centrally acting drugs for relief. Our long-term goal is to fill a major gap in the understanding of the afferent pathways mediating heartburn to enable novel strategies to relieve acid suppression-resistant pain. We will address our novel hypothesis that heartburn is mediated by a relatively unstudied nociceptor subtype, namely the vagal jugular afferent C-fibers. Our hypothesis is based on two premises: Firstly, there are two distinguishable but overlapping types of painful esophageal sensations in humans: the heartburn, which is reliably evoked by esophageal acid infusion, and esophageal pain (more similar to other types of visceral pain), which is reliably evoked by esophageal distention. Simultaneously, there are two subtypes of of esophageal C- fiber nociceptors (vagal jugular and spinal DRG) with afferent properties that favor preferential detection of acid (vagal jugular nociceptors innervating the mucosa) and mechanical distention (distention-sensitive DRG nociceptors). In Aim 1 (discovery of novel target) we will determine which vagal afferent nerve subtype(s) has peripheral nerve terminals in the esophageal mucosa such that it is likely to be exposed to luminal acid, is activated by acid, and has central terminals in the brainstem areas implicated in perceptions of visceral noxious stimuli. Vagal esophageal afferent nerves can be divided into 4 major subtypes: P2X2+/TRPV1- nodose mechanoreceptors, P2X2+/TRPV1+ nodose C-fibers acid-, Tac1+/TRPV1+ jugular nociceptors, and poorly characterized capsaicin-insensitive jugular fibers Tac1+/TRPV1-. We have developed innovative approaches to selectively express reporters in these subtypes including TRPV1-Flp crossed with P2X2-Cre or Tac1-Cre to obtained mice in which nodose or jugular subtypes can be selectively targeted by appropriate dual Flp-/Cre- sensitive AAV-vectors. In Aim 2 (validation of novel target) we will begin to evaluate the role of selective activation of only vagal jugular C-fibers (Tac1+/TRPV1+ subtype) in initiating painful sensations from the esophagus in the mouse and rat by selectively expressing the DREADD receptor hM3Dq in esophageal jugular C-fiber (Tac1+/TRPV1+) neurons and evaluating the pain-induced responses to systemic administration of hM3Dq agonist clozapine N -oxide (CNO).