Trigeminal - RVM involvement in bilateral deep tissue orofacial hyperalgesia

描述（由申请人提供）：大约1000万美国人患有颞下颌关节疾病（TMJD）。尽管口腔面部持续疼痛在人群中普遍存在，但由于缺乏对相关机制的了解，针对患者的治疗方法很少。最近，有报道表明，患有肌筋膜颞下颌关节痛或慢性颈部疼痛的患者在三叉区会出现双侧超敏反应。单侧完全性弗氏佐剂（CFA）诱导的深层组织炎症导致大鼠双侧口面部痛觉过敏。单侧将炎症细胞因子白介素-12 （IL-12）注射到三叉神经内插/尾核（VIVC）过渡区也会导致双侧口面痛觉过敏，并随着吻侧腹内侧髓质（RVM）的病变而减弱。本研究拟探讨单侧诱导的VIVC神经元的细胞因子激活、RVM神经元的激活和对侧VIVC神经元的激活是否为双侧深部组织口面痛觉过敏的发生所必需。具体目的1将研究在VIVC过渡区单侧IL-12释放对于双侧口面痛觉过敏的发展是否必要。采用cfa诱导的咬肌炎症模型，检测IL-1受体拮抗剂注入VIVC过渡区前后的机械敏感性。具体目的2将研究RVM中NK1-R的激活是否对双侧口面痛觉过敏的发展是必要的。在rvm内注射NK1-R拮抗剂后进行机械敏感性测试。免疫组织化学将用于观察可能投射到RVM的各种细胞核中SP表达的变化。特异性目的3将研究RVM中NK1-R的激活是否导致对侧VIVC中血清素能促进性下降。5-HT将通过色氨酸羟化酶-2 shRNA从RVM中的神经元中消失，5-HT3受体将被对侧VIVC中的特异性拮抗剂Y-25130阻断。将测量机械敏感性和Fos蛋白表达，以确定5-HT/5-HT3信号在对侧口面痛觉过敏发展中的作用。通过更好地了解深层组织疼痛向对侧促进的途径和机制，可能会开发出新的治疗口腔面部疼痛疾病的方法和策略。！

DESCRIPTION (provided by applicant): Approximately 10 million Americans suffer from temporomandibular joint disorders (TMJD). Despite the prevalence of orofacial persistent pain amongst the population, few treatments exist for patients due to the lack of understanding about the mechanisms involved. Recently, reports have shown that patients with myofascial TMJD or chronic neck pain experience bilateral hypersensitivity in the trigeminal region. Unilateral complete Freund's adjuvant (CFA)-induced deep tissue inflammation leads to bilateral orofacial hyperalgesia in rats. Unilateral injection of the inflammatory cytokine, interleukin-12 (IL-12) into the trigeminal subnuclei interpolaris/caudalis (VIVC) transition zone also results in bilateral orofacial hyperalgesia and is attenuated with lesions to the rostral ventromedial medulla (RVM). This study proposes to investigate whether unilaterally- induced cytokine activation of VIVC neurons, the activation of RVM neurons, and the activation of contralateral VIVC neurons are necessary for the development of bilateral deep tissue orofacial hyperalgesia. Specific aim 1 will investigate whether unilateral IL-12 release in the VIVC transition zone is necessary for the development of bilateral orofacial hyperalgesia. Using a CFA-induced inflammation model of the masseter muscle, mechanical sensitivity will be tested before and after injection of IL-1 receptor antagonist into the VIVC transition zone. Specific aim 2 will investigate whether NK1-R activation in the RVM is necessary for the development of bilateral orofacial hyperalgesia. Mechanical sensitivity will be tested after intra-RVM NK1-R antagonist microinjection following inflammation. Immunohistochemistry will be used to look at changes in SP expression in various nuclei that may project to the RVM. Specific aim 3 will investigate whether NK1-R activation in the RVM leads to descending serotonergic facilitation in the contralateral VIVC. 5-HT will be depleted from neurons in the RVM using tryptophan hydroxylase-2 shRNA and 5-HT3 receptors will be blocked with specific antagonist, Y-25130, in the contralateral VIVC. Mechanical sensitivity and Fos protein expression will be measured to determine the involvement of 5-HT/5-HT3 signaling in the development of contralateral orofacial hyperalgesia. Through better understanding of the pathways and mechanisms involved in deep tissue pain facilitation to the contralateral side, novel therapies and strategies may be developed for orofacial pain disorders. ! PUBLIC HEALTH RELEVANCE: Orofacial muscle pain related to temporomandibular joint disorders affects approximately 10-12% of the population. Referred pain (secondary pain) is a common trait amongst these patients and recently referred pain at the contralateral site has been reported with increased frequency. Little is known about the mechanisms involved in secondary hyperalgesia in the trigeminal system, which greatly diminishes the efficacy and breadth of available treatments. This study will investigate possible mechanisms involved in the development of contralateral orofacial hyperalgesia after a unilateral deep tissue injury. Understanding the mechanisms involved will enable the development of various novel therapies for the treatment of orofacial pain that may increase efficacy and decrease side effects. The application may not only apply to secondary pain but also pain at the primary source of injury.