Temporal and Qualitative Differences in the Development of Allodynic Behaviors between Mice and Rats in a Peripheral Nerve Injury Model

The spared nerve injury (SNI) model of neuropathic pain was first developed by Decosterd and Woolf in 2000 in Sprague Dawley rats to enhance reproducibility of injury and behavioral responses resulting from a partial nerve injury. Given the differences in methodology and inconsistent behavioral data published in the SNI model of neuropathic pain in mice, and given that interspecies behavioral comparisons using the same peripheral nerve injury are presently lacking, in this study we assessed the development of mechanical and cold allodynia for five weeks in C57BL/6 mice and Sprague Dawley rats that underwent SNI. In rats and mice, the tibial and peroneal branches were ligated then severed, leaving the sural branch intact. By controlling several factors in the surgical procedure and behavioral tests, we found that rats developed and maintained strong mechanical and robust cold allodynia immediately following the injury that was maintained for the duration of the experiment (five weeks). In comparison, mice developed mechanical allodynia to a lesser magnitude which peaked at 2 weeks, but did not develop cold allodynia. We found both temporal and qualitative differences in the development of allodynic behaviors between SNI-mice and SNI-rats. Parallel analysis of interspecies differences can be exploited to reveal novel molecular players leading to divergent pain behaviors.