Sleep fragmentation by brief awakenings as a surrogate to measure neuropathic spontaneous pain

项目摘要/摘要 大多数神经病理性疼痛的临床前研究几乎完全集中在机械性异位痛觉和 作为终点读数的热痛觉过敏。虽然这些都与评估刺激诱发的 过敏，他们忽略了神经病理性疼痛患者报告的两个最主要的主诉：自发性疼痛 以及睡眠障碍。目前还没有可靠地测量啮齿动物自发疼痛的技术， 限制了我们对神经性疼痛的机制和睡眠障碍的本质的研究 州政府目前还不得而知。 我们分析了两种周围神经病理性疼痛的小鼠模型的睡眠和疼痛反应，发现 虽然周围神经损伤没有改变总的睡眠时间，但它导致了严重的非快速眼动。 两种模型中的睡眠(NREMS)碎片，只有当小鼠也显示出 当诱发的疼痛敏感度恢复到损伤前的值时，异常的疼痛超敏反应得到解决。这个 睡眠片断的觉醒事件的时间分布与报告的非常短暂的剧烈疼痛发作相吻合 创伤性神经病理性疼痛患者(1)，并伴有罕见的自发性疼痛样症 三叉神经损伤后清醒啮齿动物的行为观察(2-4)。 在我们的试验数据中，我们使用了遗传和药理学方法的组合，并发现 神经损伤后睡眠碎片的增加源于受损的外周感觉神经元，而不是 似乎是由外周输入引起的，可以被镇痛剂阻断。在这个项目中，我们假设 神经损伤引起的睡眠碎片与感觉的自发活动有因果关系 激活疼痛通路的纤维，因此它可以用作替代读数 量化神经病理性自发性疼痛。 我们提出了三个特定的目标来测试神经损伤后的睡眠碎片是否由异位激活的 损伤的感觉神经元，激活上行疼痛通路，而不涉及无害的刺激或 需要引起有害的刺激。 目的1：确定神经损伤后哪些外周感觉神经元驱动NREMS碎裂。 目标2：确定负责NREMS碎裂的神经活动是否在 受伤部位或需要外界刺激。 目的3：测试脊髓-臂旁通路是否参与神经损伤所致的NREMS碎裂 因为我们不能测量活体动物的自发疼痛，所以不可能进行机械化 学习。找到一种新的神经病理性自发性疼痛的读数测量方法将代表着一个基本的 突破研究潜在的新型止痛药的潜在机制和疗效。

Project Summary/Abstract Most preclinical research on neuropathic pain has focused almost exclusively on mechanical allodynia and thermal hyperalgesia as endpoint readouts. While these are pertinent to assess stimulus-evoked hypersensitivity, they leave out the two top complaints reported by neuropathic pain patients: spontaneous pain and sleep disturbances. There is currently no technique to measure spontaneous pain reliably in rodents, limiting our study of the mechanisms responsible, and the nature of the sleep disturbances in neuropathic pain states are not known. We analyzed sleep and pain responses in two mouse models of peripheral neuropathic pain and found that while peripheral nerve trauma did not change total sleep amount, it caused a severe non-rapid eye movement sleep (NREMS) fragmentation in both models, which was only detected when mice also displayed signs of abnormal pain hypersensitivity and resolved when evoked pain sensitivity returned to pre-injury values. The temporal profile of the wake episodes that fragment sleep fits with the very brief sharp pain burst reported in patients with traumatic neuropathic pain (1), and also with the rare occurrence of spontaneous pain-like behavior observed in awake rodents after trigeminal nerve injury (2-4). In our pilot data, we used a combination of genetic and pharmacological approaches and found that the increase in sleep fragmentation after nerve injury originates from injured peripheral sensory neurons, does not appear to be caused by peripheral inputs and can be blocked by analgesics. In this project we hypothesize that sleep fragmentation caused by nerve injury is causally linked to the spontaneous activity in sensory fibers that activates pain pathways, and that therefore it could be used as a surrogate readout for quantifying neuropathic spontaneous pain. We propose 3 Specific Aims to test if sleep fragmentation after nerve injury is caused by ectopic activation of injured sensory neurons that activates ascending pain pathways, while it does not involve innocuous stimuli or require evoked noxious stimuli. Aim 1: Identify which peripheral sensory neurons drive NREMS fragmentation after nerve injury. Aim 2: Determine if the neural activity responsible for NREMS fragmentation is generated spontaneously at the injury site or requires external stimuli. Aim 3: Test if the spino-parabrachial pathway contributes to nerve injury-induced NREMS fragmentation Because we cannot measure spontaneous pain in live animals it has been impossible to perform mechanistic studies. Identifying a novel readout measure for neuropathic spontaneous pain would represent a fundamental breakthrough to study the underlying mechanisms and test the efficacy of potential novel analgesics.