Evaluation of new method to induce neuritis and comparison its symptoms with current chronic constriction injury method in male rat

Introduction: There are various animal models to investigate neuropathic pain which the most usual one is chronic constriction injury method. The aim of the present study was the evaluation of neuropathic pain following chronic spiral suturing around the sciatic nerve without ligation as a new model. Materials and Methods: Thirty Wistar male rats, weighting 180-220 gram randomly were divided into three groups as sham, chronic constriction injury (CCI), and chronic sciatic spiral suturing (CSS). CCI was performed by four loos ligation using catgut chromic suture around sciatic nerve. CSS was performed through spirally suturing of catgut chromic four times around the sciatic nerve without any ligation. In the sham group, muscle and skin were sutured after exposing the nerve. To determine mechanical allodynia and thermal hyperalgesia, Von Frey filaments and plantar test devise were used respectively every four days during three weeks. Results: CCI led to significant mechanical allodynia (P<0.01) and thermal hyperalgesia (P<0.001) compared to sham group. On the other side CSS led to a transient mechanical allodynia (P<0.05) but permanent thermal hyperalgesia (P<0.001) in comparison with sham group. Considerably, the mechanical allodynia in the CCI group was reduced significantly (P<0.01) against that in CSS group, however thermal hyperalgesia were the same in both of CCI and CSS groups. Conclusion: Chronic spiral suturing around the sciatic nerve without ligation led to thermal hyperalgesia as chronic constriction injury method, but unlike CCI method, led to a temporary mechanical allodynia.