OBJECTIVETo investigate the difference between two methods for establishing rat models of complex regional pain syndrome type 1.

METHODSTwenty-four adult SD rats were randomly allocated into control group, tibia fracture group and ischemia group (n=8), and complex regional pain syndrome type 1 was simulated in the latter two groups using different methods. The pain behaviors of the rats were observed and serum substance P level was detected with ELISA at different time points after the operations.

RESULTSLimb loss occurred in 3 rats in tibia fracture group, and the other 5 rats showed a lowered pain threshold. At 8 h after modeling, the rats in ischemia group showed more obvious reduction of pain threshold than those in tibia fracture group. Serum substance P levels in the two model groups underwent similar alterations after modeling, both significantly higher than that in the control group (P<0.01). Microcirculation changes were more serious in tibia fracture group than in ischemia group. Ulcer-like lesions were found in the skin of some rats in tibia fracture group. No obvious pathologies were observed microscopically in the sciatic nerve in the two model groups.

CONCLUSIONThe two methods can both be effective to simulate complex regional pain syndrome type 1, but tibia fracture results in more sustained symptoms and pathological changes in the microcirculation.