• Qian-Qian Zhao, Xiao-Yan Qian, Jian-Xiong An, Cai-Cai Liu, Qi-Wu Fang, Yong Wang, Yi-De Jiang, Doris K Cope, and John P Williams.
• Department of Anesthesiology, Pain Medicine & Critical Care Medicine, Aviation General Hospital of China Medical University & Beijing Institute of Translational Medicine, Chinese Academy of Sciences, Beijing, China.
• Pain Physician. 2015 Nov 1; 18 (6): E1083-90.

BackgroundA new animal model of trigeminal neuralgia produced by injecting cobra venom into the infraorbital nerve (ION) trunk in rats had been developed. We tested and extended the model by observing the ultrastructural alterations of neurons and ameliorative effect of pregabalin in cobra venom-induced pain behaviors of rats.ObjectivesThe goal of this study was to prove the feasibility of the cobra venom-induced model of trigeminal neuralgia and to demonstrate the demyelination change of ION and medulla oblongata is the major pathological change of trigeminal neuralgia.Study DesignAn experimental study.SettingDepartment of Anesthesiology, Pain Medicine, and Critical Care Medicine, Aviation General Hospital of China Medical University.MethodsExperiments were carried out on male Sprague-Dawley rats. Video recordings were taken after the cobra venom injection and pregabalin administration. Ultrastructural alterations of ION and medulla oblongata were observed at the electron microscopic level. We also observed alteration in pain behaviors by analysis of video recordings.ResultsCompared to the preoperative and sham-operated group rats, experimental group rats exhibited significant changes in exploratory, resting, face-grooming, and head-shake behaviors on 3, 7, 14 days after operation (P < 0.01). The demyelination changes of ION and medulla oblongata were evident after administration of cobra venom to the ION. Compared to the pre-treated (no pregabalin administration) and control group rats, pregabalin group rats showed profound changes in exploratory, resting, face-grooming, and head-shake behaviors throughout the 14 day study period after treatment with drugs (P < 0.01).LimitationsUltrastructural alterations of ION and medulla oblongata were not examined after the treatment with pregabalin.ConclusionsVideo recordings of free behaviors and pregabalin application prove the feasibility of the rat model of trigeminal neuralgia. The results of electron micrographs are consistent with a previous study in humans showing that the demyelination change of axons is the major pathological change of trigeminal neuralgia. The central demyelination alterations may explain why the mechanical threshold was found to be decreased on the non-operated side of experimental animals.

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