Nociceptor Maturation & Response to Peripheral Injury

描述（由申请人提供）：脊髓中的疼痛回路在胎儿晚期和出生后早期的长时间内发展，并且在此期间特别容易受到组织创伤和炎症的影响。在出生后的最初几周，有髓鞘初级传入神经的中央末梢进行了重大重组，以产生在成人背角中看到的刻板的层状终止模式。最近在新生小鼠中的研究结果表明，触觉传入在早期产生显著的成人板层终止模式，因此出生后很少进行中枢重组。相比之下，有髓鞘的伤害感受器引起广泛的，不适当的中央预测在出生后的早期生活，因此，这些传入的特征成人终止模式似乎成熟后。由于新生儿中有髓鞘伤害感受器中枢投射的相对不成熟，这组传入神经随后的出生后成熟可能对外周的早期扰动非常敏感。 拟议的实验将检查出生后的时间过程中，有髓鞘的伤害感受器达到成熟，以确定这种脆弱性的潜在窗口。这些研究将解决这一假设，即这种早期中枢旺盛通常是短暂的，但早期组织创伤，如持续性组织炎症引起的，逮捕了正常的产后重组的中央解剖，导致永久性的结构改变脊髓疼痛电路。一个孤立的体感系统制备开发的全面分析个别皮肤感觉神经元将被用来研究生后成熟的有髓鞘的伤害性感受器在有毛和无毛的皮肤的小鼠。将使用新生小鼠无毛皮肤中清洁剂诱导的炎症模型来检查早期组织创伤对单个神经元的解剖学、生理学和神经化学成熟的影响。通过细胞内记录，将使用各种天然皮肤刺激对神经元进行生理学表征，然后通过Neurobiotin的离子电渗法对其进行整体标记。他们的中央投影将被重建和形态计量学分析的变化发生在整个出生后的成熟。将对体细胞进行免疫细胞化学分析，以确定神经化学变化，并分析外周末梢的相关结构变化，在正常和创伤皮肤。这些研究的结果将提供一个详细的了解早期成熟的疼痛系统的这一重要组成部分，这些传入神经的敏感性，早期扰动。这些信息将是关键的发展，未来的战略，在儿科疼痛管理和翻译这些战略转化为有效的做法。

DESCRIPTION (provided by applicant): Pain circuitry in the spinal cord develops over a prolonged period of late fetal and early postnatal life and is particularly vulnerable to tissue trauma and inflammation during this time. Over the first few weeks of postnatal life, the central terminals of myelinated primary afferents undergo significant reorganization to generate the stereotypical laminar termination patterns seen in the adult dorsal horn. Recent findings in newborn mice have revealed that tactile afferents generate strikingly adult laminar termination patterns early on and thus undergo little central reorganization postnatally. By contrast, myelinated nociceptors give rise to widespread, inappropriate central projections in early postnatal life and thus the characteristic adult termination patterns of these afferents appear to mature later. Due to the relative immaturity of myelinated nociceptor central projections in newborns, the subsequent postnatal maturation of this group of afferents may be acutely susceptible to early perturbations of the periphery. The proposed experiments will examine the postnatal time course over which myelinated nociceptors achieve maturity to determine the potential window of this vulnerability. These studies will address the hypothesis that this early central exuberance is normally transient but that early tissue trauma, such as that caused by persistent tissue inflammation, arrests the normal postnatal reorganization of their central anatomy, leading to permanent structural alterations in spinal pain circuitry. An isolated somatosensory system preparation developed for comprehensive analyses of individual skin sensory neurons will be used to study the postnatal maturation of myelinated nociceptors in both hairy and glabrous skin of mice. A model of adjuvant-induced inflammation in glabrous skin of newborn mice will be used to examine the effects of early tissue trauma on the anatomical, physiological, and neurochemical maturation of individual neurons. Through intracellular recordings, neurons will be physiologically characterized using a variety of natural skin stimuli and then labeled in their entirety through iontophoresis of Neurobiotin. Their central projections will be reconstructed and analyzed morphometrically for changes taking place throughout postnatal maturation. Somata will be analyzed immunocytochemically to determine neurochemical changes, and peripheral endings will be analyzed for correlated structural changes in both normal and traumatized skin. The results of these studies will provide a detailed understanding of the early maturation of this vital component of the pain system, and the susceptibility of these afferents to early perturbation. This information will be pivotal to the development of future strategies in pediatric pain management and the translation of these strategies into effective practice.