COMPARISON OF 3 RODENT NEUROPATHIC PAIN MODELS

To characterize various animal models of neuropathic pain, we compared three previously developed rat models using the same behavioral testi ng methods. These models involve: (I) chronic constriction injury by l oose ligation of the sciatic nerve (CCI); (2) tight ligation of the pa rtial sciatic nerve (PSL); and (3) tight ligation of spinal nerves (SN L). Comparisons were made for the time course of behavioral signs repr esenting various components of neuropathic pain as well as for the eff ects of surgical sympathectomy. In general, all three methods of perip heral nerve injury produced behavioral signs of both ongoing and evoke d pain with similar time courses. However, there was a considerable di fference in the magnitude of each pain component between models. Signs of mechanical allodynia were largest in the SNL injury and smallest i n the CCI model. On the other hand, behavioral signs representing ongo ing pain were much more prominent in the CCI model than in the other t wo. Although the behavioral signs of neuropathic pain tended to decrea se after sympathectomy in all three models, the change was most eviden t in the SNL model. The results of the present study suggest that the three rat models tested have contrasting features, yet all are useful neuropathic pain models, possibly representing different populations o f human neuropathic pain patients.