Synaptic Function within Mature Central Pain Networks after Neonatal Injury

尽管越来越多的证据表明，在生命早期的关键时期，组织损伤会加剧疼痛， 新生儿创伤的细胞和分子机制， 'prime'发育中的伤害感受通路仍不清楚。此外，虽然成人中的抑制性中间神经元 已知脊髓背角（DH）由调节不同方面的多个亚群组成 在感觉加工过程中，抑制性中间神经元的类别对形成疼痛敏感性很重要， 新生儿的身份还有待确认。最后，新生儿损伤引发疼痛的程度 通过破坏抑制性DH神经元的特定亚群的成熟， 上行脊髓投射神经元的前馈抑制还有待阐明。长期目标是 通过促进我们对慢性疼痛的理解，促进设计适合年龄的策略来治疗慢性疼痛。 中枢伤害感受网络的发育神经生物学。本申请的目的是阐明 早期组织损伤对脑内已识别的抑制性突触回路成熟的影响 脊髓DH中心假设是新生儿组织损伤破坏了初级传入神经的发育 驱动表达强啡肽（DYN）的中间神经元介导上行投射的前馈抑制 神经元，这有助于引发脊髓伤害性回路随后的损伤。的基本原理 拟议的研究是，通过对不同脊椎动物的出生后发育产生新的见解， 在正常和病理条件下的抑制回路，这些研究将奠定概念基础， 新的治疗方法，以年龄特异性的方式限制脊髓疼痛网络的输出， 最大限度地减少新生儿损伤对发育中的CNS的长期不良影响。以强为导 根据初步数据，将检验中心假设，并通过以下方式实现本申请的总体目标： 追求以下具体目标：（1）确定早期组织损伤如何塑造初级传入驱动， 发育中DH的抑制性中间神经元;（2）鉴定介导前馈的DH中间神经元 在正常和病理条件下抑制发育中的脊髓投射神经元;和（3）鉴定 发育中DH的抑制性中间神经元，其抑制疼痛的能力受到新生组织的损害 损伤这些目标将通过使用多学科实验方法来实现，包括 体外电生理学、光遗传学、化学遗传学、行为学和免疫组织化学技术。的 这些研究的结果将是对早期组织损伤如何改变功能的第一次深入了解。 在发育中的脊髓伤害性网络中抑制性微电路的组织，从而减少 抑制痛觉的能力因此，拟议的研究是有意义的，因为它将确定 脊髓DH内的特定抑制性突触通路，其必须最终恢复，以便 防止新生儿组织损伤后对慢性疼痛过度敏感。

Despite growing evidence that tissue damage during a critical period of early life can exacerbate pain severity following subsequent injury, the cellular and molecular mechanisms by which neonatal trauma can ‘prime’ developing nociceptive pathways remain unclear. Furthermore, while inhibitory interneurons in the adult spinal dorsal horn (DH) are known to be comprised of multiple subpopulations which regulate distinct aspects of sensory processing, the classes of inhibitory interneurons that are important for shaping pain sensitivity in the neonate have yet to be identified. Finally, the degree to which neonatal injury primes developing pain circuits by disrupting the maturation of specific subpopulations of inhibitory DH neurons necessary for feedforward inhibition of ascending spinal projection neurons has yet to be elucidated. The long-term goal is to facilitate the design of age-appropriate strategies to treat chronic pain by advancing our understanding of the developmental neurobiology of central nociceptive networks. The objective of this application is to elucidate the consequences of early tissue injury for the maturation of identified inhibitory synaptic circuits within the spinal DH. The central hypothesis is that neonatal tissue damage disrupts the development of primary afferent drive to dynorphin-expressing (DYN) interneurons mediating feedforward inhibition of ascending projection neurons, which contributes to the priming of spinal nociceptive circuits to subsequent injury. The rationale of the proposed research is that by yielding novel insight into the postnatal development of distinct spinal inhibitory circuits under normal and pathological conditions, these studies will lay a conceptual foundation for new therapeutic approaches to restrict the output of the spinal pain network in an age-specific manner and minimize the adverse long-term effects of neonatal injury on the developing CNS. 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) Determine how early tissue damage shapes primary afferent drive to inhibitory interneurons in the developing DH; (2) Identify the DH interneurons which mediate feedforward inhibition of developing spinal projection neurons under normal and pathological conditions; and (3) Identify the inhibitory interneurons in the developing DH whose ability to suppress pain is compromised by neonatal tissue injury. These aims will be accomplished by using a multidisciplinary experimental approach that includes in vitro electrophysiological, optogenetic, chemogenetic, behavioral and immunohistochemical techniques. The outcome of these investigations will be the first insight into how early tissue damage alters the functional organization of inhibitory microcircuits in the developing spinal nociceptive network and thereby diminishes their ability to suppress pain sensation. As a result, the proposed research is significant because it will identify the specific inhibitory synaptic pathways within the spinal DH that must ultimately be restored in order to prevent the exaggerated susceptibility to chronic pain following neonatal tissue damage.