Comparative Study of Chronic Postischemic Pain Models in Mice: O-Ring Versus Tie Method

摘要

Background: The success rate for the production of animal models of chronic postischemia pain(CPIP) using an O-ring has yet to be improved in the study of complex regional pain syndrome-typeI (CRPS-I), and producing a CPIP model is challenging, especially for mice.Objectives: We devised a new CPIP model with a higher success rate that induces ischemia for 3hours by tying the hind limbs of mice with a rubber band, followed by reperfusion.Study Design: A randomized, controlled animal trial.Methods: Twenty-two male C57BL/6 mice were divided into a sham (n = 6), a ring (n = 8), anda tie group (n = 8). Anesthesia was induced using isoflurane. A precut O-ring was mounted onthe upper left ankle in the sham group. A tight-fitting O-ring and a push-pull gauge manometerwere mounted at the same location in the ring and tie groups, respectively. Reperfusion wasinduced 3 hours later. The thickness and circumference of the hind paws were measured beforeischemia induction. Measurements were repeated 10 days after reperfusion. Mechanical allodyniawas measured with a von Frey filament until 12 weeks after reperfusion.Results: The new tie model required 5 additional days until the onset of allodynia compared withthe existing CPIP O-ring model. However, the successful induction rate of CPIP was higher in thetie group than in the ring group, and allodynia was maintained for over 30 days in the tie group.The ring and tie groups exhibited significantly high levels of tumor necrosis factor-alpha than thosein the sham group.Limitations: First, we did not evaluate hyperalgesia, cold or heat allodynia. Second, we did notmeasure blood levels of inflammatory or antiinflammatory cytokines, and research on oxidativestress biomarkers such as isoprostane, 8-hydroxy-2’-deoxyguanosine (a marker of DNA oxidativedamage), and malondialdehyde was not performed.Conclusions: The new CPIP tie model has a higher rate of successful induction than existingO-ring models for mice, with longer duration of mechanical allodynia. The model may reduce thenumber of animals sacrificed in CRPS-I research and could be useful for studying long-term effectsof drugs.