Abstract: PURPOSE: To establish a new animal model of trigeminal neuralgia（TN） produced by administration of talc to peripheral infraobital nerve in rats. METHODS: Thirty male Wistar rats were randomly divided into 2 groups. Talcum powder (30%,0.3 mL) was injected into the peripheral infraorbital foramen in one group, the same dose of normal saline was injected by the same method in another group. On 3 day before surgery and 3 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 6 weeks, 8 and 12 weeks postoperatively, mechanical pain behavior was determined. Statistical analysis of the threshold of pain response was performed and the behavior of pain was observed in the area of infraorbital nerve innervation in rats. Histopathological changes of the peripheral infraorbital nerve tissue in the rats were observed 3 days, 4 weeks, 8 weeks and 12 weeks postoperatively. The expression of inflammatory factors such as tumor necrosis factor-α (TNF-α) and interleukin -1β (IL-1β) in the territory of the infraorbital nerve was detected by immunohistochemistry. SPSS16.0 software package was used to analyze the data. RESULTS: The mechanical pain threshold of rats in the infraorbital innervation area 3 days postoperatively in the experimental group was significantly decreased compared with that in the preoperative group and the control group (P<0.01). The rats in the experimental group 3 days postoperatively experienced symptoms of irritability, scratching the face or aggressive behavior. Twelve weeks after operation, the mechanical pain threshold was still significantly decreased. Histopathological examination in the experimental group 3 days postoperatively mainly showed inflammation with a few inflammatory factors（IL-1β and TNF-α）expression. Inflammation in the experimental group 1week postoperatively was more intense and more inflammatory factors were expressed. Four weeks postoperatively, there was more proliferation of granulation tissue in the area of peripheral infraorbital nerve tissue and expression of inflammatory factors was highest. Four to twelve weeks, the inflammatory response in the experimental group was gradually reduced, increased scar and infraorbital nerve compressing by scar were observed, and the expression of inflammatory factors decreased gradually. CONCLUSIONS: Injection of talc to the peripheral infraorbital foramen can establish a reliable and stable animal model for research of etiology and treatment of TN.

Key words: Talc, Trigeminal neuralgia, Animal model, Rat