Establishment of a rat model of trigeminal neuralgia induced by photochemical nerve injury / 中国药理学通报

ABSTRACT

Aim To investigate the behavioral changes of the pain related neuromodulation and neurotransmission in peripheral and central nervous systems in rats with trigeminal neuralgia (TN)and provide a disease relevant animal model for mecha-nism study of TN.Methods The male SD rats were randomly divided into sham operation group and TN surgical group.The latter group was further divided into model group and gabapentin group (100 mg · kg-1 ). TN was induced by intravenous erythrosine B injection and laser irradiation.The pain behavior of rats was evaluated using mechanical pain threshold measured with Von Frey hairs.Fluorescence quantitative PCR technique was deployed to study the change of Tac1 mRNA expressions in trigeminal ganglia.Utilizing microdialysis technique followed by high performance liquid chromatography fluorescence detection (HPLC-FLD),the extracellular striatum fluid was collected and glutamate(Glu)concentration was determined.Results In the model group,the average mechanical pain threshold in facial ar-ea innervated by the trigeminal nerve remained below 4g after 7 days post surgery.The mechanical threshold of the model group (1.63 ±1.27)g was significantly lower (P<0.01)than the control group (24.17 ±4.49)g on day10 post surgery.In gen-eral,the mechanical withdraw threshold was decreased from the preoperative value of 26g to the postoperative value of (1.60 ± 1.74)g (P<0.01),and maintained stable at (0.71 ±1.24) g during the whole dynamic monitoring period from day7 to day60.The successful rate of this model was 63%.After sur-gery,Tac1 mRNA expression in trigeminal ganglia and extracel-lular Glu levels in striatum were significantly up-regulated (P<0.05 ) in the model group. Animals receiving Gabapentin showed significant improvement in pain symptoms,as well as re-ductions of Tac1 mRNA expression in trigeminal ganglia and ex-tracellular Glu concentration in striatum (P<0.05 ).Conclu-sions The above described photochemically induced TN rat model can partially mimic the clinical TN symptoms and its pathophysiology.Considering its overall high stability,it is very likely that this model could be used in preclinical mechanism study or drug screening of TN.