ABSTRACT
BACKGROUND: Because genetic manipulation is commonly accomplished in mice, mouse models for pain have advanced our understanding of the mechanisms of persistent pain. The purpose of this experimental study is to develop a mouse model for understanding incision induced postoperative pain. METHODS: A longitudinal incision was made at the hindpaw of male DBA/2 mice. The withdrawal frequency (WF) from applications of von Frey filaments and the response frequency (RF) to blunt mechanical stimulation were examined in an incision group and a control group. The withdrawal latency (WL) to radiant heat and a pain score based on weight bearing were also measured. Tests were performed 1 day before incision, and 2 hours, 1.3 days, 5 days and 7 days after incision. RESULTS: The WF for the strongest filament was 35.0 +/- 9.1% before incision and this increased to 100.0 +/- 0% at 2 hours and to 65.0 +/- 9.1% at 7 days after incision. The RF to the blunt stimulus was 4.1 +/- 4.1% before incision and 100.0 +/- 0.0% at 2 hours and 42.8 +/- 10.8% at 7 days after incision. The WL was 6.6 +/- 0.5 sec before incision and 2.4 +/- 0.3 sec at 2 hours and 5.9 +/- 0.6 sec at 7 days after incision. The pain score increased from 1.1 +/- 0.8 to 7.4 +/- 1.5 at 2 days after incision. CONCLUSIONS: A mouse model of acute postoperative pain was developing by making a surgical incision in the mouse hindpaw. Mechanical hyperalgesia and allodynia lasting for several days demonstrate that this model has similarities to the human post-operative pain state. Future studies will allow us to further investigate the genetic and molecular mechanisms of incisional pain.