Changes in expression of NRF-1 in spinal cord during remifentail-induced hyperalgesia in a rat model of incisional pain

Objective To evaluate the changes in the expression of NRF-1 in the spinal cord during remifentail-induced hyperalgesia in a rat model of incisional pain.Methods Forty-eight Sprague-Dawley rats,weighing 180-220 g,were randomly divided into 4 groups (n =12 each) using a random number table:control group (C); incisional pain group (group Ⅰ); remifentanil group (group R); incisional pain + remifentanil group (group Ⅰ + R).All the rats were anesthetized with sevoflurane.A 1-cm longitudinal incision was made through skin,fascia and muscle of the plantar aspect of the right hindpaw in I and I + R groups.In C and I groups,normal saline was subcutaneously infused for 30 min.In group I + R,remifentanil (0.04 mg/kg,0.4ml) was subcutaneously infused for 30 min starting from the onset of skin incision.Paw withdrawal threshold to mechanical stimulation (PWMT) was measured at 24 h before operation and at 2,6,12,24 and 48 h after operation.After measurement of PWMT at 48 h,the rats were sacrificed and L4,5 segments of the spinal cord were removed rapidly to detect the expression of nuclear respiratory factor 1 (NRF-1) by immunofluorescence and Western blot.Results Compared with group C,PWMT was significantly decreased at each time point after operation,and the expression of NRF-1 in the spinal cord was up-regulated in I and I + R groups (P ＜ 0.05).Compared with group I,PWMT was significantly decreased at each time point after operation,and the expression of NRF-1 in the spinal cord was up-regulated in group I + R (P ＜ 0.05).Conclusion Up-regulation of NRF-1 expression in the spinal cord may be involved in the development of remifentail-induced hyperalgesia in a rat model of incisional pain. Key words: Piperidines;  Hyperalgesia;  Spinal cord;  Nuclear respiratory factor 1