Department of Neurosurgery, the 309th Hospital of Chinese People's Liberation Army, Beijing, China.
Department of Neurology, the 456th hospital of PLA, Jinan, PR China; Department of Human Anatomy & K.K. Leung Brain Research Centre, Preclinical School of Medicine, the Fourth Military Medical University, Xi'an, PR China.
Pain Physician. 2018 Sep;21(5):E555-E564.
Over-expression of spinal protein kinase Cγ(PKCγ) contributes to the induction of persistent bilateral hyperalgesia following inflammatory injury, yet the role of spinal PKCγ in short- and long-lasting pain behavior is poorly understood.
This study aimed to characterize the contribution of spinal PKCγ to spontaneous pain and long-lasting bilateral hyperalgesia in formalin-induced inflamed mice using pharmacological inhibition.
Laboratory animal study.
The study was performed in the Department of Human Anatomy and K.K. Leung Brain Research Centre, Preclinical School of Medicine, the Fourth Military Medical University (Xi'an, China) and the Department of Anesthesiology, Fuzhou General Hospital (Fuzhou, China).
Male mice were unilaterally intraplantarly injected with formalin to induce inflammatory pain. Spontaneous pain behaviors, including flinches and lickings, were recorded by off-line video during the first hour post-injection and counted. Using von Frey tests, long-lasting bilateral mechanical paw withdrawal thresholds were determined before injection and at indicated time points thereafter. Temporal expression of spinal PKCγ was observed by immunohistochemical staining. For pharmacological inhibition, mice were treated daily with intrathecal Tat carrier or selective PKCγ inhibitor KIG31-1, from 1 hour prior to 10 days after formalin injection. Spontaneous pain behaviors and long-lasting bilateral mechanical hyperalgesia were assessed. Spinal PKCγ expression was also observed by using immunohistochemical staining and western blot.
The number of PKCγ-immunoreactive (ir) spinal neurons was significantly higher at 10 days, but not 2 hours, after formalin intraplantar injection, and accompanied by long-lasting bilateral hyperalgesia. Furthermore, long-lasting bilateral hyperalgesia could be reversed by pharmacological inhibition of over-expressed spinal PKCγ; however, pretreating with intrathecal KIG31-1 showed no antinociceptive effects on short-term spontaneous pain behaviors.
All results were obtained from the mice and no PKCγ inhibitors were available through clinical practice. Therefore, it remains difficult to draw definitive connections between animal research and human application.
Our findings suggest that spinal PKCγ plays a predominant role in long-lasting bilateral hyperalgesia, but not in the spontaneous pain behaviors induced by formalin.
Formalin, spontaneous pain, mechanical hyperalgesia, protein kinase C gamma, KIG31-1, mice.
脊髓蛋白激酶 Cγ（PKCγ）的过度表达有助于炎症损伤后持续双侧痛觉过敏的诱导，但脊髓 PKCγ 在短期和长期疼痛行为中的作用知之甚少。
本研究旨在使用药理学抑制来表征脊髓 PKCγ对福尔马林诱导的炎性小鼠自发性疼痛和长期双侧痛觉过敏的贡献。
实验室动物研究。
该研究在第四军医大学（中国西安）人体解剖学系和 K.K.梁脑研究中心、临床医学前学校以及福州总医院（中国福州）麻醉科进行。
雄性小鼠单侧足底注射福尔马林诱导炎症性疼痛。通过离线视频记录注射后第 1 小时内的自发性疼痛行为，包括抽搐和舔舐，并进行计数。使用 von Frey 测试，在注射前和之后的指定时间点确定长期双侧机械性足底撤回阈值。通过免疫组织化学染色观察脊髓 PKCγ 的时间表达。对于药理学抑制，从小鼠接受 Tat 载体或选择性 PKCγ 抑制剂 KIG31-1 鞘内治疗开始，从福尔马林注射前 1 小时持续到 10 天后。评估自发性疼痛行为和长期双侧机械性痛觉过敏。还通过免疫组织化学染色和 Western blot 观察脊髓 PKCγ 的表达。
福尔马林足底注射后 10 天（而非 2 小时），脊髓 PKCγ 免疫反应（ir）神经元数量显著增加，同时伴有长期双侧痛觉过敏。此外，过度表达的脊髓 PKCγ 的药理学抑制可逆转长期双侧痛觉过敏；然而，鞘内给予 KIG31-1 预处理对短期自发性疼痛行为没有镇痛作用。
所有结果均来自小鼠，且临床实践中无法获得 PKCγ 抑制剂。因此，动物研究与人类应用之间仍然难以建立明确的联系。
我们的研究结果表明，脊髓 PKCγ 在长期双侧痛觉过敏中起主要作用，但在福尔马林诱导的自发性疼痛行为中不起作用。
福尔马林、自发性疼痛、机械性痛觉过敏、蛋白激酶 Cγ、KIG31-1、小鼠。
