Colon afferents: molecular identity, histology/morphology and hypersensitivity

描述(申请人提供)：肠易激综合征(IBS)估计影响高达15%的美国人口，对生活质量和每年约300亿美元的直接和间接医疗费用产生负面影响。疼痛是IBS的特征症状，也是患者去看胃肠医生的主要原因。越来越多的证据表明，来自结直肠传入的高外周感觉输入(即传入敏化)对于IBS相关疼痛和超敏的持续是必要的。这项研究的目的是研究大肠中功能不同的传入类别的分子/神经化学特性(化学型)和组织位置，从而揭示导致大肠超敏反应的传入敏化机制。具体地说，一种新的具有连续神经和脊髓的小鼠结肠直肠的体外制备将用于将传入电生理学的功能研究与化学类型评估和传入末梢解剖相结合。研究将在长期模型的背景下进行，内脏高敏感性分别由酵母多糖或三硝基苯磺酸(TNBS)引起。提出了三个具体目标。具体目标1将描述盆腔神经(PN)结直肠神经传入的不同功能类别的化学类型。具体目标2将确定在TE PN结直肠神经支配中不同类型传入的组织位置和形态特征。具体目标3将使用计算机模拟来探索大肠传入神经编码增强的潜在机制。具体目标4将通过体外研究人类肠道传入，探索将上述研究结果转化为治疗结直肠疼痛和超敏反应的临床靶点的可能性。结合功能、化学典型和形态方法，将可以产生与传入敏化有关的通道/受体的新信息，并首次揭示大肠感受性末梢的组织学/形态特征。实验数据将用于构建和验证计算机模拟，这将允许探索每个功能不同的传入类敏化的假定机制(S)。所提出的实验结果有可能指导具有大肠传入亚类特异性的药物化合物的开发策略。

DESCRIPTION (provided by applicant): Irritable bowel syndrome (IBS) is estimated to affect up to 15% of the population in the USA, with negative effects on quality of life and annual direct and indirect health care costs of ~30 billion U.S. dollars. Pain is the characteristic symptom of IBS and the main reason for patient visits to gastroenterologists. Accumulating evidence suggests that heightened peripheral sensory input from colorectal afferents (i.e., afferent sensitization) is necessary for the persistence of IBS-related pain and hypersensitivity. The goal of the proposed research is to investigate molecular/neurochemical identities ('chemotype') and histological locations of functionally distinct afferent classes in the colorectum, from which information about mechanisms of afferent sensitization that contribute to colorectal hypersensitivity will be revealed. Specifically, a novel ex vivo preparation of the mouse colorectum with nerves and spinal cord in continuity will be used to couple functional study of afferent electrophysiology with chemotype evaluation and afferent ending anatomy. Studies will be done in the context of long-term models of visceral hypersensitivity induced by intracolonic treatment with zymosan or trinitrobenzene sulfonic acid (TNBS), respectively. Three specific aims are proposed. Specific Aim 1 will characterize chemotype of functionally distinct classes of afferents in the pelvic nerve (PN) colorectal innervation. Specific Aim 2 will determine the histological location and morphological features of functionally distinct classes of afferents in te PN colorectal innervation. Specific Aim 3 will explore the underlying mechanisms for enhanced neural encoding of colorectal afferents using computational simulation. Specific Aim 4 will explore the possible translation of outcomes from the foregoing studies into clinic targets for management of colorectal pain and hypersensitivity by studying human intestinal afferents in vitro. The combined functional, chemotypical, and morphological approaches will allow generation of new information about channels/receptors that contribute to afferent sensitization and, for the first time, reveal histological/morphological features of colorectal receptive endings Experimental data will be used to construct and validate a computational simulation, which will allow exploration of the putative mechanism(s) for sensitization in each functionally distinct afferent class. The outcomes of the proposed experiments have the potential to guide strategies for development of pharmacological compounds that possess colorectal afferent sub-class specificity.