Dissection of the Organizational Differences Between Paw and Trunk Pain Circuits

爪子和躯干疼痛回路之间组织差异的剖析

• 批准号: 9107242
• 负责人: William Paul Olson
• 金额: $ 4.36万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2018-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9107242
• 关键词: Animals; Area; Body Regions; Calcium; Color; Complex; Data; Development; Discrimination; Dissection; Dorsal; Esthesia; Fiber; Functional Imaging; Genetic; Genetic Recombination; Genetic Vectors; Goals; Hand; Health; Human; Image; In Vitro; Individual; Label; Light; Limb structure; Location; Measures; Mechanoreceptors; Mediating; Modeling; Morphology; Mus; Neurons; Nociception; Nociceptors; Pain; Peripheral; Population; Proteins; Sensory; Skin; Spinal Cord; Stimulus; System; Tactile; Tamoxifen; Testing; Touch sensation; Viral Vector; adeno-associated viral vector; base; beta-Alanine; body position; chronic back pain; chronic pain; density; fovea centralis; human data; insight; nerve supply; neural circuit; novel; public health relevance; receptive field; red fluorescent protein; regional difference; research study; segregation; tool

 DESCRIPTION (provided by applicant): Chronic pain is a costly and complex human health problem. While many chronic pain conditions are region specific (chronic back pain, for instance), we currently know very little about regional differences in pain circuit organization. I was recently discovered that the human fingertips have the best acuity (i.e. can detect fine spatial detail) for pain stimuli compared to other body regions. However, the human fingertips have a lower density of nociceptive fibers compared to other skin areas, raising the question of how a skin area with a low innervation density displays high sensory acuity. My lab recently generated a new inducible Cre mouse line (MrgDCreERT2) that allows for genetic tracing of individual non-peptidergic nociceptors. While paw skin and trunk skin nociceptors have similar peripheral receptive field sizes, after sparse nociceptor labeling, I found that their spinal cord projections display a different morphology (paw nociceptors have rounded central terminals while trunk nociceptors have long and thin central terminals). This finding suggests that nociceptors innervating the hand form different neural circuits from those innervating the proximal limb/trunk skin. I propose to determine if, and how, pain circuits representing the paw and trunk of mice are differently organized. While my preliminary experiments suggest that spinal cord terminal morphologies (round and long) are segregated based on body position (paw-vs.-trunk), these experiments have not excluded the possibility that these morphologies instead belong to different functional subtypes. In Aim 1, I will further test the hypothesis that paw and trunk nociceptors have different morphologies by performing higher density nociceptor labeling to determine if these terminal types remain segregated. Further, to exclude the possibility that these terminal morphologies belong to functionally distinct subpopulations, I will test if a major distinguisher of non-peptidergic nociceptor subtypes (sensitivity to itch-causing beta-alanine) correlates with terminal morphology by combining genetic tracing with calcium imaging. In Aim 2, I will test the hypothesis that paw and trunk nociceptor circuits have different rates of overlap between neighboring nociceptor skin and/or spinal cord terminals. I will use a combination of genetic and viral vector tools to label neighboring nociceptors with different fluorescent proteins. I will then measure overlap rates between neighboring nociceptor terminals and compare these rates between paw and trunk circuits. In summary, these experiments will be the first to elucidate key circuit differences between paw and trunk nociceptors and could provide a likely mechanism to explain the high spatial acuity of the fingertips for pain.

 描述（由申请人提供）：慢性疼痛是一个代价高昂且复杂的人类健康问题。虽然许多慢性疼痛状况具有特定区域性（例如慢性背痛），但我们目前对疼痛回路组织的区域差异知之甚少。我最近发现，与其他身体区域相比，人类指尖对疼痛刺激具有最佳的敏锐度（即可以检测到精细的空间细节）。然而，与其他皮肤区域相比，人类指尖的伤害性纤维密度较低，这就提出了一个问题：神经支配密度低的皮肤区域如何表现出高感觉敏锐度。我的实验室最近培育了一种新的诱导型 Cre 小鼠品系 (MrgDCreERT2)，可以对个体非肽能伤害感受器进行基因追踪。虽然爪子皮肤和躯干皮肤伤害感受器具有相似的外周感受野大小，但在稀疏伤害感受器标记后，我发现它们的脊髓投影显示出不同的形态（爪子伤害感受器具有圆形的中央末端，而躯干伤害感受器具有长而薄的中央末端）。这一发现表明，支配手部的伤害感受器形成与支配近端肢体/躯干皮肤的伤害感受器不同的神经回路。我建议确定代表小鼠的爪子和躯干的疼痛回路是否以及如何以不同的方式组织。虽然我的初步实验表明脊髓末端形态（圆形和长形）根据身体位置（爪子与躯干）进行分离，但这些实验并没有排除这些形态属于不同功能亚型的可能性。在目标 1 中，我将通过执行更高密度的伤害感受器标记来进一步测试爪子和躯干伤害感受器具有不同形态的假设，以确定这些末端类型是否保持隔离。此外，为了排除这些终端形态属于功能不同的亚群的可能性，我将 通过将遗传追踪与钙成像相结合，测试非肽能伤害感受器亚型（对引起瘙痒的β-丙氨酸的敏感性）的主要区别是否与末端形态相关。在目标 2 中，我将检验以下假设：爪子和躯干伤害感受器回路有不同 相邻伤害感受器皮肤和/或脊髓末端之间的重叠率。我将结合使用遗传和病毒载体工具，用不同的荧光蛋白标记邻近的伤害感受器。然后，我将测量相邻伤害感受器终端之间的重叠率，并比较爪子和躯干电路之间的这些重叠率。总之，这些实验将首次阐明爪子和躯干伤害感受器之间的关键回路差异，并可能提供一种可能的机制来解释指尖对疼痛的高空间敏锐度。