Comparison of pain behavior responses in two peripheral neuropathic models (SNI, CCI) in rat

Introduction: Peripheral nerve injury leads to neuropathic pain syndromes and different sensation like allodynia and hyperalgesia. Different animal models of neuropathic pain are used to study the neuropathic pain mechanisms. The present study was performed on two models, (SNI). The purpose of this study was comparing the behavioral responses of yhese two models and the role of saphenous and sural nerve in SNI model. Methods: Male Wistar rats (180-220 g) were used. CCI models were made by 4 loose legations on common sciatic nerve. In SNI models, 2 of 3 terminal branches of sciatic nerve were cut and the sural nerve was remained intact. Zero, 4, 7 and 14 days after the operation, thermal hyperalgesia and mechano allodynia were assessed with radiant heat with von-frey filament. Results: The results indicated mechano allodynia and thermal hyperalgesia at days 4th, 7th and 14th. In comparison of SNI and CCI, there was no significant difference in pain behaviors however there was more sensitivity to allodynia in the SNI model and more sensitivity to hyperalgesia in the CCI model. Saphenous territory showed less allodynia and hyperalgesia than sural territory. Conclusion: behavioral testes of CCI and SNI models demonstrated the hypersensitivity to both thermal and mechanical stimuli. But there were different pain intensity between the sural and saphenous nerve territories in SNI model. It seems different neuropathy models have different mechanisms and symptoms.