Neuronal Excitability and Motility in Colitis

描述（由申请人提供）：肠壁上的神经元控制肠道对摄入食物的反应；它们还调节消化、营养吸收和废物消除的过程。在炎症性肠病（IBD）中，肠道功能的各种特征，包括运动、分泌和敏感性都发生了改变。由于肠道的神经细胞调节所有这些功能，很可能是这些神经元的变化引起了导致患者痛苦的症状。在过去的3年里，我们以循序渐进的方式评估了炎症引起的结肠回路变化，我们已经确定了三个部位的基本变化：(1)粘膜层血清素可用性增加；(2)内禀感觉神经元亢奋；(3)神经元间突触信号的易化。提出的实验旨在阐明这些变化的机制，这些变化如何影响结肠运动，以及炎症恢复后持续存在的变化。在具体的目标1中，我们将使用电生理学和分子方法来测试内在感觉神经元的高兴奋性涉及到中间电导的下调，Ca2+激活的K*通道和超极化激活的阳离子通道的上调。在具体目标2中，我们将使用电生理学和电子显微镜，通过检测肌肠丛突触前神经递质释放、突触后敏感性和神经末梢密度的变化来研究突触促进的机制。在具体的目标3中，我们将研究结肠蠕动、时空运动模式和神经肌肉反应，以确定炎症诱导的反射回路中的哪些变化有助于改变结肠运动以及这是如何发生的。在具体的目标4中，我们将测试炎症诱导的神经可塑性和相关的运动性变化是否在炎症恢复后持续存在。这些变化是标准诊断程序无法检测到的，并且可能是炎症性肠病缓解期和炎症后肠易激综合征（IBS）期间肠道功能改变的基础。将使用一系列技术，包括细胞内电压和电流记录、实时定量聚合酶链反应、电子显微镜和数字增强运动性分析。通过这种方式，我们将提供炎症结肠中神经传递的独特、综合/翻译视图。这些研究结果都是高度可行的，它们将增强我们对炎症结肠病理生理学的理解，并将提高我们对肠易激综合征的理解。

DESCRIPTION (provided by applicant): Neurons in the wall of the intestine control how the gut reacts to an ingested meal; they also regulate the processes of digestion, nutrient absorption, and waste elimination. In inflammatory bowel disease (IBD), various features of gut function, including motility, secretion and sensitivity are altered. As nerve cells of the bowel regulate all of these functions, it is likely that changes in these neurons cause the symptoms that lead to the suffering experienced by afflicted individuals. In the past 3 years, we have evaluated inflammation-induced changes along the circuitry of the colon in a step-wise fashion, and we have identified fundamental changes at three sites in particular: (1) increased serotonin availability in the mucosal layer; (2) intrinsic sensory neuron hyperexcitability; and (3) facilitation of synaptic signals between neurons. The proposed experiments are designed to elucidate the mechanisms that underlie these changes, how these changes affect colonic motility, and what changes persist following recovery from inflammation. In specific aim 1, we will use electrophysiology and molecular approaches to test the hypothesis that intrinsic sensory neuron hyperexcitability involves down-regulation of intermediate conductance, Ca2+activated K* channels and an up-regulation of hyperpolarization-activated cation channels. In specific aim 2, we will use electrophysiology and electron microscopy to investigate the mechanisms of synaptic facilitation by testing for changes in presynaptic neurotransmitter release, postsynaptic sensitivity and nerve terminal density in the myenteric plexus. In specific aim 3, we will study colonic peristalsis, spatiotemporal motility patterns and neuromuscular responses to determine which inflammation-induced changes in the reflex circuitry contribute to altered colonic motility and how this occurs. In specific aim 4, we will test whether inflammation-induced neuroplasticity and related changes in motility persist beyond recovery from inflammation. Such changes would be undetectable by standard diagnostic procedures, and could underlie altered gut function during remission from inflammatory bowel disease and in post-inflammatory irritable bowel syndrome (IBS). An array of techniques will be used, including intracellular voltage and current recordings, real time quantitative polymerase chain reaction, electron microscopy, and digitally enhanced motility assays. In this way, we will provide a unique, integrated/translational view of neurotransmission in the inflamed colon. The findings of these investigations, all of which are highly feasible, will enhance our understanding of the pathophysiology of the inflamed colon, and they will improve our comprehension of IBS.