Experimental Study On The Establishment Of A New Animal Model Of Trigeminal Neuralgia Produced By Administration Of Talc Around The Infraorbital Nerve In The Rat

Objective:To establish a simple,easy and reliable animal model of trigeminal neuralgia which is suitable for clinical research.Methods:Experiment 1:20 male Wistar rats were randomly divided into two groups.One group was injected with talcum powder(30%,0.3ml),while the other group was injected with the same dose of saline.On the 3 day before surgery and postoperative 3 day,1 week,2 weeks,3 weeks,4 weeks,6 weeks,8 and 12 weeks,mechanical pain behavior is determined.The threshold of pain response and the behavior of pain are observed in the area of infraorbital nerve innervation in rats.Experiment 2:20 male Wistar rats were randomly divided into two groups.One group was injected with talcum powder(30%,0.3ml),while the other group was injected with the same dose of saline.We use video recording behavior of rats 3 days before surgery and postoperative 1 week,2 weeks,,4 weeks.The camera was placed in front of the cage 1 meters to record the number and time of exploratory behavior,static behavior,grasping the face behavior,head shaking behavior,licking hind and licking body behavior.Experiment 3: 20 Wistar rats were randomly divided into two groups: the group with talcum powder injection and the control group(10 in every group).According to the method of Experiment 1,the trigeminal neuralgia model was established.Histopathological changes and demyelinating staining of infraorbital nerve tissue and the medulla tissue in the rats were observed on the postoperative 3 day,4 weeks,8 weeks and 12 weeks respectively.The expression of tumor necrosis factor-?(TNF-?)and interleukin-1?(IL-1?)in the territory of the infraorbital nerve and Substance P and beta-Endorphin(?-EP)in the medulla oblongata were detected by using immunohistochemistry.Results: 1,The mechanical pain threshold of rats in the infraobital innervation area on the postoperative 3 day in the experimental group was significantly decreased compared with that in the preoperative group and the control group(P?0.01).The rats on the postoperative 3 day in the experimental group expressed symptoms of irritability,scratching the face or aggressive behavior.The mechanical pain threshold decreased until 12 weeks after operation.2,The video display: changes of exploratory behavior,static behavior,grasping face behavior,head shaking behavior in the experimental group rats on the postoperative 3 day was statistically significant,compared with the control and preoperative group(P?0.01).But behavior of licking hind legs and licking the body had no obvious changes on the postoperative 3 day.The changes of the exploratory behavior,the static behavior,thegrasping face behavior and head shaking behavior of the rats were more obvious on the postoperative 1 week,2weeks and 4weeks,and there was statistical significance compared with the control and preoperative group(P?0.01).There was no significant difference in the behavior of licking hind legs and licking body compared with the control and preoperative group.3,The histopathological observation in the experimental group on the postoperative 3 day is mainly inflammatory manifestation,such as few inflammatory factor expression.The inflammation in the experimental group on the postoperative 1week was more intense and there is a few inflammatory factor expression by using immunohistochemistry.The expression of inflammatory factor on the Postoperative 4weeks in the experimental group was the most highest.The inflammatory response on the Postoperative 4-12 weeks in the experimental group was gradually reduced,but the local scar increased,which can result in the visible compression of infraorbital nerve whose appearance of demyelination was demonstrated by demyelination staining method.No significant change of the expression of neurotransmitter such as Substance P and beta-Endorphin(?-EP)in the medulla was found on the Postoperative 3day-3weeks in the experimental group.The expression of neurotransmitter of pain in the medulla increased obviously on the Postoperative 4weeks-12 weeks in the experimental group by using immunohistochemistry.The medulla oblongata demonstrated obvious manifestation of demyelination on the Postoperative 4weeks-12 weeks in the experimental group.Conclusion: 1.The injection of talc into the surroundings of infraorbital nerve can cause pain hypersensitivity in the area of the infraorbital nerve,spontaneous pain and and the related behavioral changes.2.Histopathological and immunohistochemical results showed that pain was caused by inflammatory factors in the animal model in the early stage,and was caused by the compression of the infraorbital nerve in the later period.3.The animal model,which is simple and easy,can induce pain in the early period and has long duration.Therefore,it is an ideal animal model of trigeminal neuralgia.