Mechanism of Nociception Induced by Innocuous Cold in Trigeminal System

摘要：三叉神经病理性疼痛是最令人衰弱的疼痛障碍，但目前的治疗方法 包括阿片类药物在内的药物对大多数患者无效。这种疼痛通常是由一口凉气引起的 吹到脸上的空气。降温时三叉神经病理性疼痛加重的机制是 不是很清楚，这阻碍了我们设计基于机械的治疗方法来有效地治疗这种疾病 毁灭性的痛苦。我们最近在大鼠模型上的研究表明，温度敏感的两孔结构域K+ 热通道(K2Ps)在降温时三叉神经病理性疼痛加重中起关键作用 温度。我们这里的中心假设是：1)热K2P提供刹车以防止伤害性感受器 生理条件下的过度兴奋，2)三叉神经损伤导致热性K2P下降。 导致三叉神经伤害性感受器过度兴奋和神经病理性疼痛的刹车受损规则，以及3) 降温进一步抑制热K2Ps导致三叉神经病理性疼痛加重。我们 我将用以下具体目标来检验这些假设。♦目标1.阐明热K2Ps在 控制三叉神经伤害性感受器兴奋性并确定降温温度对K2P的影响 功能。我们将使用免疫组织化学方法来表征三叉神经痛感受器中热K2P的表达。 正常大鼠。我们将使用我们新开发的原位膜片钳记录来表征热K2P- 三叉神经伤害性感受器介导的泄漏K+电流及其在三叉神经伤害性感受器兴奋性控制中的作用 正常大鼠。我们将研究降温对三叉神经伤害性感受器热K2P功能的影响 正常大鼠。♦目的2.阐明三叉神经损伤下调热K2P表达导致 三叉神经伤害性感受器过度兴奋。我们将使用两个已建立的三叉神经病理性疼痛的大鼠模型， 眶下神经慢性压迫性损伤与奥沙利铂所致三叉神经病 模特们。我们将研究热K2P表达和热K2P介导的泄漏K+电流的变化。 这些模型的三叉神经痛感受器。我们将使用药理学和遗传学方法来阐明 热K2Ps的下调导致三叉神经伤害性感受器的过度兴奋。我们将决定如何 降温进一步加剧了这些模型大鼠三叉神经伤害性感受器的过度兴奋性。♦Aim 3. 阐明热K2P下调是三叉神经病理性疼痛的基础，并建立热K2Ps。 作为治疗大鼠三叉神经病理性疼痛的靶点。我们将使用口腔面部操作测试来研究 热K2P下调是否导致三叉神经病理性疼痛，表现为冷性超敏和 痛觉过敏。我们将使用离子-CCI和奥沙利铂模型来确定三叉神经病理性疼痛 可通过三叉神经热K2P功能的药理和遗传增强而缓解 传入神经。♦这些目标的完成将填补三叉神经伤害性感受的科学空白，阐明新的 三叉神经病理性疼痛的机制，并为这种衰弱疼痛建立新的治疗靶点。

ABSTRACT: Trigeminal neuropathic pain is the most debilitating pain disorder but current treatments including opiates are not effective for it in most patients. The pain can often be triggered by a breath of cooling air blowing on the face. Mechanisms of trigeminal neuropathic pain exacerbation at cooling temperatures are not well understood, which prevents us from designing mechanistically based therapy to effectively treat this devastating pain. Our recent studies in rat models have suggested that thermally sensitive two-pore domain K+ channels (thermal K2Ps) may play a key role in trigeminal neuropathic pain exacerbation at cooling temperatures. Our central hypotheses here are: 1) Thermal K2Ps provide a brake to prevent nociceptor hyperexcitability under physiological conditions, 2) Trigeminal nerve injury causes thermal K2P down- regulation to impair the brake leading to trigeminal nociceptor hyperexcitability and neuropathic pain, and 3) Cooling temperatures further suppress thermal K2Ps to lead to trigeminal neuropathic pain exacerbation. We will test these hypotheses with the following specific aims. ♦Aim 1. Elucidate the role of thermal K2Ps in controlling trigeminal nociceptor excitability and determine the effects of cooling temperatures on K2P functions. We will use immunohistochemistry to characterize thermal K2P expression in trigeminal nociceptors of normal rats. We will use our newly developed in situ patch-clamp recordings to characterize thermal K2P- mediated leak K+ currents in trigeminal nociceptors and their role in controlling trigeminal nociceptor excitability of normal rats. We will study effects of cooling temperatures on thermal K2P functions in trigeminal nociceptors of normal rats. ♦Aim 2. Elucidate that trigeminal nerve injury down-regulates thermal K2P expression leading to trigeminal nociceptor hyperexcitability. We will use two established rat models of trigeminal neuropathic pain, the infraorbital nerve chronic constrictive injury (ION-CCI) and oxaliplatin-induced trigeminal neuropathy models. We will study changes of thermal K2P expression and thermal K2P-mediated leak K+ currents in trigeminal nociceptors of these models. We will use pharmacological and genetic approaches to elucidate that down-regulation of thermal K2Ps leads to trigeminal nociceptor hyperexcitability. We will determine how cooling temperatures further exacerbate hyperexcitability of trigeminal nociceptors of these rat models. ♦Aim 3. Elucidate that thermal K2P down-regulation underlies trigeminal neuropathic pain, and establish thermal K2Ps as therapeutic targets for trigeminal neuropathic pain in rat models. We will use orofacial operant tests to study whether thermal K2P down-regulation leads to trigeminal neuropathic pain manifested with cold allodynia and hyperalgesia. We will use ION-CCI and oxaliplatin models to determine whether trigeminal neuropathic pain can be alleviated by pharmacological and genetic enhancements of thermal K2P functions in trigeminal afferent nerves. ♦ Completion of these Aims will fill the scientific gap of trigeminal nociception, elucidate a new mechanism of trigeminal neuropathic pain, and establish new therapeutic targets for this debilitating pain.