A novel pathway mediating the development of chronic orofacial neuropathic pain

描述(申请人提供)：慢性口腔面部疼痛是一种常见的临床综合征，由于慢性口腔面部疼痛的细胞机制尚不清楚，因此缺乏特定和有效的治疗药物。根据我们在三叉神经损伤模型和非口面部疼痛模型上的初步数据，我们假设三叉神经损伤诱导了三叉神经节(TG)和相关的脑干/上颈脊髓(VC/C2)的血栓反应蛋白-4(TSP4)的表达，从而导致感觉神经元的过度兴奋性，以及脊髓中三叉神经复合体的异常突触发生。这些变化为三叉神经损伤向慢性疼痛发展的过渡奠定了基础。在这项研究中，我们计划确定TSP4在调节行为超敏反应和脊髓神经元超兴奋性方面的关键结构域(S)。病毒驱动的TSP4在TG或VC/C2中的表达将被用来确定TSP4在慢性疼痛处理中的S作用部位。我们将通过共聚焦显微镜和电子显微镜来确定神经损伤模型中异常突触发生的程度。此外，下行调节通路和电压门控钙通道对TSP4介导的行为超敏和背角神经元超兴奋性的影响将分别用药物进行研究。TSP4对感觉神经元兴奋性、钙通道活性和细胞内钙信号的影响将在神经损伤模型的分离神经元或完整TG中或在TSP4处理后进行研究。为了确定TSP4是否通过与其受体--钙通道α-2-增量-1亚单位(Cava2d1)的相互作用，以感觉神经元特异性的方式诱导行为超敏反应和背角神经元的超兴奋性，我们将使用Cava2d1条件基因敲除小鼠进行这些研究。本研究的最终目的是确定三叉神经损伤后TSP4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.