Developmental Regulation of Intrinsic Excitability in Spinal Pain Networks

描述(申请人提供)：尽管很明显，即使是最小的婴儿也会因为受伤、疾病、手术或重症监护治疗而经历巨大的疼痛，但关于组织损伤如何影响中枢神经系统(CNS)中正在发育的疼痛回路中神经元的内在兴奋性，人们知之甚少。由于脊髓浅背角(SDH)在疼痛通路中起着关键的中继站的作用，更好地了解不同年龄的组织损伤如何影响SDH神经元的固有膜特性是解决这一问题的重要和合乎逻辑的第一步。长期目标是通过寻找更适合发育的新的止痛策略来改善婴儿和儿童疼痛的临床治疗。这项应用的总体目标是确定在正常和病理条件下调节SDH内发育中神经元内在兴奋性的关键离子电导，这是追求这一目标的下一步。中心假说是，在出生后早期发育的关键时期，I层内的兴奋性中间神经元表现出内在的起搏型振荡，这种振荡由持续的Na+和Ca~(2+)电流驱动，并受到新生组织损伤的促进。这项拟议的研究的基本原理是，了解不成熟的伤害性回路中固有的神经元兴奋性是如何被具体调控的，将揭示调节其输出的新方法，而这在成人的研究中并不明显。在强大的初步数据的指导下，中心假设将得到检验，这一应用的总体目标将通过追求以下具体目标来实现：1)确定出生后早期自发活跃的SDH神经元；(2)阐明驱动新生SDH神经元内在放电的离子机制；以及(3)检测早期组织损伤后发育中的SDH网络内离子通道表达和内在兴奋性的细胞类型特异性变化。这些目标将通过使用体外电生理、免疫组织化学和生化技术来表征已确定的发育中的SDH神经元亚型的神经元兴奋性的离子机制，并确定这些固有的膜特性在多大程度上受到组织损伤的调节，以一种年龄依赖的方式。这些研究的结果将是对未成熟的脊柱疼痛网络中的活动如何在细胞水平上进行控制的新见解。因此，这项拟议的研究具有重要意义，因为它将开始提供开发慢性儿科疼痛循证治疗所需的知识。

DESCRIPTION (provided by applicant): Although it is clear that even the youngest infants can experience significant pain as the result of injury, disease, surgery or intensive care therapy, little is known about how tissue damage affects the intrinsic excitability of neurons within developing pain circuits in the central nervous system (CNS). Since the superficial dorsal horn of the spinal cord (SDH) functions as a critical relay station in the pain pathway, a better understanding of how the intrinsic membrane properties of SDH neurons are influenced by tissue injury at different ages represents an important and logical first step towards addressing this issue. The long-term goal is to improve the clinical treatment of pain in infants and children by identifying novel analgesic strategies which are more developmentally appropriate. The overall objective of this application, which is the next step in pursuit of that goal, is to identify the key ionic conductances which regulate the intrinsic excitability of developing neurons within the SDH under normal and pathological conditions. The central hypothesis is that excitatory interneurons within lamina I exhibit intrinsic, pacemaker-type oscillations during a critical period of early postnatal development, which are driven by persistent Na+ and Ca2+ currents and facilitated by neonatal tissue damage. The rationale of the proposed research is that understanding how intrinsic neuronal excitability is specifically regulated within immature nociceptive circuits will reveal new ways to modulate their output which would not be evident from studies in the adult. Guided by strong preliminary data, the central hypothesis will be tested and the overall objective of this application achieved by pursuing the following specific aims: 1) Identify the SDH neurons which are spontaneously active during early postnatal development; (2) Elucidate the ionic mechanisms which drive the intrinsic firing of neonatal SDH neurons; and (3) Detect cell-type-specific changes in ion channel expression and intrinsic excitability within the developing SDH network following early tissue damage. These aims will be accomplished by using in vitro electrophysiological, immunohistochemical and biochemical techniques to characterize the ionic mechanisms regulating neuronal excitability in identified subtypes of developing SDH neurons and determine the extent to which these intrinsic membrane properties are modulated by tissue injury in an age-dependent manner. The outcome of these investigations will be new insight into how activity within immature spinal pain networks is controlled at the cellular level. As a result, the proposed research is significant because it will begin to provide the knowledge needed to develop evidence- based treatments for chronic pediatric pain.