Nociceptor Maturation & Response to Peripheral Injury

描述(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较长时间内发展，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，有髓初级传入的中央终末经历了重大的重组，产生了在成人背角看到的典型的板层终末模式。在新生小鼠身上的最新发现表明，触觉传入在早期产生惊人的成人板层终止模式，因此在出生后几乎没有经历中央重组。相比之下，有髓伤害性感受器在出生后早期会产生广泛的、不适当的中枢投射，因此这些传入的特有的成人终止模式似乎成熟得更晚。由于新生儿有髓伤害性感受器中枢投射的相对不成熟，这类传入神经在出生后的随后成熟可能对早期的外周干扰非常敏感。 拟议的实验将检查有髓伤害性感受器达到成熟的出生后时间过程，以确定这一漏洞的潜在窗口。这些研究将解决这样的假设，即这种早期的中枢兴奋通常是短暂的，但早期组织创伤，例如由持续性组织炎症引起的创伤，阻止了出生后正常的中枢解剖重组，导致脊髓痛觉回路的永久性结构变化。为全面分析单个皮肤感觉神经元而开发的分离体感系统制剂将用于研究小鼠有毛和无毛皮肤中有髓伤害性感受器的出生后成熟。新生小鼠无毛皮肤佐剂诱导的炎症模型将被用来检测早期组织创伤对单个神经元的解剖、生理和神经化学成熟的影响。通过细胞内记录，神经元将使用各种自然皮肤刺激进行生理学表征，然后通过神经生物素的离子导入进行整体标记。他们的中央投射将被重建并进行形态计量学分析，以了解整个出生后成熟过程中发生的变化。将对胞体进行免疫细胞化学分析，以确定神经化学变化，并将分析周围末梢，以寻找正常和创伤皮肤的相关结构变化。这些研究的结果将对疼痛系统的这一重要组成部分的早期成熟以及这些传入细胞对早期扰动的敏感性提供详细的了解。这些信息将对未来儿科疼痛管理战略的制定和将这些战略转化为有效实践至关重要。

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.