Mechanism of Nociception Induced by Innocuous Cold in Trigeminal System

摘要：三叉神经病理性疼痛是最使人衰弱的疼痛疾病，但目前的治疗方法 包括阿片类药物对大多数患者无效。这种疼痛通常会由一口清凉的空气引发 空气吹在脸上。三叉神经病理性疼痛在低温下恶化的机制是 这使得我们无法设计基于机制的疗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中的研究表明，热敏双孔结构域K+ 通道（热K2 Ps）可能在三叉神经病理性疼痛恶化中起关键作用 温度。我们的中心假设是：1）热K2 Ps提供了一个制动器，以防止伤害感受器 生理条件下的过度兴奋，2）三叉神经损伤导致热K2 P下降- 调节以损害导致三叉神经伤害感受器过度兴奋和神经性疼痛的制动，以及3） 冷却温度进一步抑制热K2 Ps，导致三叉神经痛恶化。我们 我们将以下列具体目标来检验这些假设。1.阐明热K2 Ps在 控制三叉神经伤害感受器的兴奋性，并确定冷却温度对K2 P的影响 功能协调发展的我们将使用免疫组织化学来表征三叉神经伤害感受器中的热K2 P表达， 正常的老鼠我们将使用我们新开发的原位膜片钳记录来表征热K2 P- 三叉神经伤害性感受器介导的漏钾电流及其在控制三叉神经伤害性感受器兴奋性中的作用 正常的老鼠我们将研究冷却温度对三叉神经伤害感受器中热K2 P功能的影响 正常的老鼠第二章.阐明三叉神经损伤下调热K2 P表达，导致 三叉神经伤害感受器过度兴奋我们将使用两种已建立的三叉神经病理性疼痛大鼠模型， 眶下神经慢性缩窄性损伤与奥沙利铂诱发三叉神经病变 模型我们将研究细胞中热K2 P表达和热K2 P介导的漏K+电流的变化 这些模型的三叉神经伤害感受器。我们将使用药理学和遗传学的方法来阐明， 热K2 Ps的下调导致三叉神经伤害感受器过度兴奋。我们将决定如何 冷却温度进一步加剧了这些大鼠模型的三叉神经伤害感受器的过度兴奋性。第三章. 阐明热K2 P下调是三叉神经病理性疼痛的基础，并建立热K2 P 作为三叉神经痛大鼠模型的治疗靶点。我们将使用口面操作性测试来研究 热K2 P下调是否会导致三叉神经病理性疼痛，表现为冷异常性疼痛， 痛觉过敏我们将使用ION-CCI和奥沙利铂模型来确定三叉神经痛是否 可以通过三叉神经中热K2 P功能的药理学和遗传学增强来缓解 传入神经这些目标的完成将填补三叉神经伤害感受的科学空白，阐明一个新的 三叉神经病理性疼痛的机制，并建立这种衰弱性疼痛的新的治疗靶点。

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.