• Jian-Xiong An, Ying He, Xiao-Yan Qian, Jian-Ping Wu, Yi-Kuan Xie, Qu-Lian Guo, John P Williams, and Doris K Cope.
• Department of Anesthesiology, Central South University Xiangya Hospital, Changsha, China. anjianxiong@yahoo.co
• Anesth. Analg.. 2011 Sep 1;113(3):652-6.

BackgroundUnderstanding the mechanism of trigeminal neuralgia may be elucidated by developing laboratory animal models that closely mimic the features of this specific type of neuropathic pain. We have developed an experimental animal model for trigeminal neuralgia using a technique of injecting cobra venom into the infraorbital nerve (ION) trunk.MethodsMale Sprague-Dawley rats were subjected to the administration of cobra venom or saline into the ION trunk. Mechanical stimuli were applied to the ION territory in consecutive days after surgery. Mechanical thresholds were measured over a 90-day period on the bilateral facial region. Vascular permeability in the ION territory was measured using Evans blue dye.ResultsThe cobra venom-treated rats developed mechanical allodynia 3 days after surgery that lasted for 60 days postoperatively at the ipsilateral side. The mechanical thresholds of the contralateral ION territory also showed a profound decrease but were sustained for only approximately 30 days. There was no change of mechanical thresholds in the control groups. The extravasation of Evans blue increased significantly in the skin after administration of cobra venom to the ION compared with control rats (P < 0.05).ConclusionThe cobra venom model may provide a reasonable model for investigating the mechanism of trigeminal neuropathic pain.

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