背根神经节Aβ神经元簇放电介导神经病理性触诱发痛机制研究

Tactile allodynia, defined as a strong nociceptive response provoked by an innocuous mechanical stimulus, is one of the common features of neuropathic pain, but its mechanisms is still keep unclear. We found that a new firing pattern- - -long-term evoked-bursting (EB) in injured A-beta dorsal root ganglion (DRG) neurons,triggered by innocuous stimuli form its peripheral sensory area, correlated with tactile allodynia behavior and also agreed with clinic allodynia symptom, suggesting that EB may be a cellular mechanism for tactile allodynia. Previous studies have shown that phenotypic switching from unnociceptive to nociceptive neurons synthesized and released pain-related neurotransmitter in Aβ neurons might account for tactile allodynia in neuropathic pain induced by peripheral nerve injury. Whether neurotransmitter phenotypic switching in EB neurons contributes to tactile allodynia remains unclear. In this proposal, base on our previous study, we will investigate the roles and its molecular mechanisms of EB neurons in tactile allodynia induced by chronic compression of DRG through combined electrophysiological, molecular biological, and behavioral methods.

触诱发痛是难以治疗的神经病理痛病症，特点是非痛刺激引起令人难以忍受的剧痛，对其发病机制至今了解甚少。我们在损伤的背根神经节(DRG)Aβ神经元记录到一种新的放电模式-诱发簇放电（EB），它是外周感受野刺激产生动作电位传导至DRG胞体诱发胞体产生的长时程簇放电，出现率与触诱发痛行为明显相关，且反应模式契合临床上触诱发痛的病痛特征，推测其可能是触诱发痛的细胞学基础，但产生机制及其作用尚不清楚；有研究显示外周神经损伤后，部分Aβ神经元可出现神经递质转型，即原本传导非痛刺激的Aβ神经元合成和释放与传导痛信息相关的神经递质，EB神经元是否可以通过递质转型参与触诱发痛的发生也不清楚。本研究我们拟以EB放电作为切入点，结合电生理、分子生物学等多种研究手段，在我们原有工作基础上进一步明确EB放电在触诱发痛中的重要作用及其产生和维持的分子机制。

本课题我们以背根神经节超兴奋Aβ神经元为切入点，从单个神经元水平阐明此类神经元离子通道、细胞内信号转导通路的改变及EB神经元递质转录、表达及末梢释放的变化。本项目以SD大鼠为研究对象，采用背根节慢性压迫方法制备慢性背根节压迫（CCD）神经病理性痛模型，并通过细胞内记录、膜片钳等电生理方法识别具有与触诱发痛相关放电模式-诱发簇放电（evoked bursting, EB）的背根节神经元，以单个神经元为研究目标，进一步采用形态学、神经生物学、分子生物学等实验手段及多项观察指标。研究结果显示1.KCNQ钾电流参与CCD术后Aβ神经元兴奋性的改变。2．在研究中发现DRG慢性压迫损伤后，DRG Aβ神经元自发放电的发生率增加，而且大鼠背根节神经元自发放电对脊髓背角广动力神经元放电活动有直接的影响。3.一种介导钾电流的slack通道参与背根节神经元兴奋性的改变