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.
Animals ; Hot Temperature ; Humans ; Hyperalgesia ; Male ; Mice ; Pain, Postoperative ; Weight-Bearing

BACKGROUND: Chronic neuropathic pain is often associated with altered immune function and the modulated immune cell response play a role in neuropathic pain by experimental nerve injury. In order to assess the possible changes in lymphocytes function following peripheral mononeuropathy, this study examined the lymphocyte subpopulation of the spleen using the monoclonal antibodies against the membrane surface markers in neuropathic BALB/c mice by a partial transection of sciatic nerve (PST). METHODS: After confirming tactile allodynia by paw withdrawal threshold, the splenic lymphocytes were stained with fluorescein isothiocyanate (FITC)-conjugated anti-mouse CD45R/B220 (B cell) and CD4 (helper/inducer T cell) or with phycoerythrin (PE)-conjugated anti-mouse CD90.2 (total T cell) and CD8 (suppressor/cytotoxic T cell). The proportions of subsets were analyzed using a FACScan laser flow cytometry system on postoperative day 5 and day 18 respectively. RESULTS: PST induced a mechanical allodynia as verified by the von Frey test at both 5 and 8 days postoperatively compared to pre-surgery (P < 0.05). Lymphocyte subpopulation was affected by PST. The proportion of CD4+ subset was significantly larger in the PST group than in the sham operated group on day 5, while the proportion of CD8+ subset was larger on day 18. In the PST group, there were significantchanges in the proportion of CD4+ on day 5 and in the proportion of CD8+ on day 18 (P < 0.05) compared to pre-surgery. There were no significant fluctuations in the proportion of total splenic T cell and B cell subsets of PST group compared to sham operated group. CONCLUSIONS: These results suggest that development of mononeuropathy is responsible for the proportional changes in splenic lymphocyte subsets in mice.
Animals ; Antibodies, Monoclonal ; B-Lymphocyte Subsets ; Flow Cytometry ; Fluorescein ; Hyperalgesia ; Lymphocyte Subsets* ; Lymphocytes* ; Membranes ; Mice* ; Mononeuropathies ; Neuralgia ; Peripheral Nerve Injuries* ; Peripheral Nerves* ; Phycoerythrin ; Sciatic Nerve ; Spleen*