A novel pathway mediating the development of chronic orofacial neuropathic pain

描述（由申请人提供）：慢性口面疼痛是一种常见的临床综合征，由于对慢性口面疼痛的细胞机制知之甚少，因此缺乏特异性和有效的治疗药物。基于我们的初步数据，从三叉神经损伤模型和非口面疼痛模型，我们假设，三叉神经损伤诱导血小板反应蛋白-4（TSP-4）的表达在三叉神经节（TG）和相关的脑干/上颈脊髓（Vc/C2），导致感觉神经元过度兴奋，和异常的突触发生在三叉神经复合体在脊髓。这些变化是从三叉神经损伤到慢性疼痛发展的转变的基础。在这项提议中，我们计划确定TSP 4在介导行为超敏反应和脊髓神经元过度兴奋中的关键结构域。分别在TG或Vc/C2中的病毒驱动的TSP 4表达将用于鉴定TSP 4在慢性疼痛处理中的作用位点。我们将进行共聚焦和电子显微镜检查，以确定神经损伤模型中异常突触发生的程度。此外，将使用相应的药物研究下行调节途径和电压门控钙通道对TSP 4介导的行为超敏性和背角神经元过度兴奋性的影响。将在分离的神经元或来自神经损伤模型的完整TG中或在TSP 4处理后研究TSP 4对感觉神经元兴奋性、钙通道活性和细胞内钙信号传导的影响。为了确定TSP 4是否以感觉神经元特异性方式通过其与其受体（钙通道α-2-δ-1亚基（Cava 2d 1））的相互作用诱导行为超敏性和背角神经元过度兴奋性，在感觉神经元亚群中选择性缺失Cava 2d 1的Cava 2d 1条件性敲除小鼠将用于这些研究。所提出的研究的最终目标是确定三叉神经损伤后TSP 4介导的向慢性疼痛状态转变的外周和/或中枢机制。

DESCRIPTION (provided by applicant): Chronic orofacial pain is a common clinical syndrome lacking specific and effective therapeutic agents due to the fact that cellular mechanisms of chronic orofacial pain are poorly understood. Based on our preliminary data from a trigeminal nerve injury model and in non-orofacial pain models, we hypothesize that trigeminal nerve injury induced thrombospondin-4 (TSP4) expression in trigeminal ganglia (TG) and associated brainstem/upper cervical spinal cord (Vc/C2) that causes sensory neuron hyperexcitability, and abnormal synaptogenesis in the trigeminal complex in the spinal cord. These changes underlie the transition from trigeminal nerve injury to chronic pain development. In this proposal, we plan to identify the critical domain(s) of TSP4 in mediating behavioral hypersensitivity and spinal neuron hyperexcitability. Viral driven TSP4 expression in TG or Vc/C2, respectively, will be used to identify the site of the TSP4's action in chronic pain processing. We will perform confocal and electron microscopy to determine the extent of abnormal synaptogenesis in the nerve injury models. In addition, the influence of descending modulatory pathways and voltage-gated-calcium channels on TSP4-mediated behavioral hypersensitivity and dorsal horn neuron hyperexcitability will be studies using respective drugs. The influence of TSP4 on sensory neuron excitability, calcium channel activities, and intracellular calcium signaling will be studied in isolated neurons or intact TG from nerve injury models, or after TSP4 treatment. To determine if TSP4 induces behavioral hypersensitivity and dorsal horn neuron hyperexcitability through its interactions with its receptor, the calcium channel alpha-2-delta-1 subunit (Cava2d1), in a sensory neuron specific manner, Cava2d1 conditional knockout mice with selective deletion of Cava2d1 in subpopulation of sensory neurons will be used for these studies. The final goal of the proposed studies is to identify the peripheral and/or central mechanisms underlying TSP4-mediated transition to chronic pain states after trigeminal nerve injury.