Anatomical and Functional Characterization of Gastrointestinal to Spinal Cord Circuits

项目摘要/摘要：内脏感觉是内脏和神经之间的沟通 系统。内脏感觉信号从胃肠道(GI)传递到中枢神经系统 迷走神经节和背根神经节(DRG)神经元。虽然胃肠道的迷走神经支配相当多 尽管研究很充分，但对支配胃肠道的DRG神经元的了解要少得多。支配结肠的DRG神经元是至关重要的 用于正常的胃肠功能。这些神经元检测胃肠道的化学物质/肠道微生物含量，调制长时间的- 胃肠道运动的范围控制，并负责传递无害(非疼痛)和有害(疼痛) 胃肠道的感觉。 最近的研究已经确定了支配结肠的DRG神经元的五种主要亚型，由它们的 结肠的解剖神经支配模式和体外对刺激的反应。支配结肠的背根节神经元 将与胃肠道相关的信息传输到脊髓。这些神经元投射到脊髓的多个板层。 背角，被认为是将信息从胃肠道传递到一系列脊髓中间神经元和 投射神经元，包括突触后背柱(PSDC)投射神经元。然而，很少有研究表明 探讨脊髓内支配结肠的背根节神经元中枢支的解剖结构。此外， 全面了解支配结肠的背根节神经元向其发送的脊髓神经元类型 它们发出的不同信号还有待探索。最后，很少有研究研究脊柱在体内的反应。 穿过背角板层的脊髓神经元对非痛性和痛性胃肠道刺激有反应。 这项建议的目的是描述结肠的中央形态和突触后伙伴- 支配背根神经节神经元。我推测，支配结肠的DRG神经元中枢支将形成不同的 基于它们传递的感觉信息的类型的形态亚型。我预测会影响结肠神经 表达机械敏感离子通道Piezo2的DRG神经元将投射到背侧更深的板层 角将无害的感觉传递给多种类型的脊髓神经元。相反，我预测多肽能症， 表达降钙素基因相关肽(Calca)α形式的结肠支配的DRG神经元将 将疼痛刺激传递到板层I/II中间神经元。我进一步假设PSDC神经元将接受 来自结肠的无害和有害的感觉信息，通过与结肠的直接和间接连接- 支配背根神经节神经元。使用条件小鼠遗传学、外科手术、病毒标记、成像、光遗传学和 在活体电生理学方法中，我将：1)表征中央树枝和突触后伙伴 脊髓中支配结肠的DRG神经元类型；2)鉴定脊髓的活体反应特性 脊髓神经元对无害和有害的结肠刺激。这些实验将从根本上推进我们 背根神经节对负责检测、传递和处理感觉的脊髓回路的理解 从结肠开始。这项研究将为胃肠道疼痛提供关键的洞察力，并可能确定新的治疗靶点。

Project Summary/Abstract: Viscerosensation is the communication between internal organs and the nervous system. Viscerosensory signals are transmitted from the gastrointestinal (GI) tract to the central nervous system by both vagal and dorsal root ganglia (DRG) neurons. While vagal innervation of the GI tract is considerably well-studied, far less is known about GI-innervating DRG neurons. Colon-innervating DRG neurons are critical for normal GI function. These neurons detect the chemical/gut microbial contents of the GI tract, modulate long- range control of GI motility, and are responsible for transmitting innocuous (non-painful) and noxious (painful) sensations from the GI tract. Recent studies have identified five major subtypes of colon-innervating DRG neurons, defined by their anatomical innervation patterns in the colon and ex vivo responses to stimuli. Colon-innervating DRG neurons transmit GI-relevant information to the spinal cord. These neurons project to multiple laminae of the spinal cord dorsal horn and are proposed to transmit information from the GI tract to a range of spinal cord interneurons and projection neurons, including postsynaptic dorsal column (PSDC) projection neurons. However, few studies have explored the anatomical organization of colon-innervating DRG neuron central arbors in the spinal cord. Further, a comprehensive understanding of the spinal cord neuron types to which colon-innervating DRG neurons send their diverse signals has yet to be explored. Finally, few studies have investigated the in vivo responses of spinal cord neurons across dorsal horn laminae to non-painful and painful GI stimuli. The goal of this proposal is to characterize the central morphologies and postsynaptic partners of colon- innervating DRG neurons. I hypothesize that colon-innervating DRG neuron central arbors will form distinct morphological subtypes based on the types of sensory information they transmit. I predict that colon-innervating DRG neurons that express the mechanosensitive ion channel, Piezo2, will project to deeper laminae of the dorsal horn to transmit innocuous sensations to multiple spinal cord neuron types. Conversely, I predict that peptidergic, colon-innervating DRG neurons that express the alpha form of Calcitonin Gene-Related Peptide (Calca) will transmit painful stimuli to laminae I/II interneurons. I further hypothesize that PSDC neurons will receive innocuous and noxious sensory information from the colon, through direct and indirect connections with colon- innervating DRG neurons. Using conditional mouse genetics, surgical, viral labeling, imaging, optogenetic and in vivo electrophysiological approaches, I will: 1) characterize the central arbors and postsynaptic partners of colon-innervating DRG neuron types in the spinal cord, and 2) identify the in vivo response properties of spinal cord neurons to innocuous and noxious colon stimuli. These experiments will advance our fundamental understanding of DRG to spinal cord circuits responsible for detecting, transmitting, and processing sensations from the colon. This research will provide critical insight, and may identify novel therapeutic targets, for GI pain.