Role of spinal c-Jun N-terminal kinase signaling pathway in incisional pain in rats

Objective To evaluate the role of spinal c-Jun N-terminal kinase (JNK) signaling pathway in incisional pain in rats. Methods Sixty-three adult male Sprague-Dawley rats, weighing 200-250 g, were randomly divided into 3 groups (n=21 each) using a random number table: incisional pain group (IP group), dimethyl sulfoxide (DMSO) group, and JNK inhibitor SP600125 group (SP group). A 1-cm longitudinal incision was made through skin, fascia and muscle of the plantar aspect of the hindpaw in anesthetized rats.In group DMSO, 10% DMSO 10 μl was injected intrathecally at 30 min before surgery.In group SP, SP600125 25 μg (in 10 μl of 10% DMSO) was injected intrathecally at 30 min before surgery.Six rats in each group were sacrificed, and the mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 24 h before establishment of the model and 2, 6, 24, 48 and 72 h after establishment of the model.After measurement of the pain threshold at 24 h before establishment of the model and 6, 24, 48 and 72 h after establishment of the model, the lumbar segment of the spinal cord was removed for determination of the expression of phosphorylated JNK (p-JNK) by immunofluorescence. Results The MWT was significantly lower, the TWL was shorter, and the expression of p-JNK was lower at each time point after establishment of the model than at 24 h before establishment of the model in group IP (P 0.05). Conclusion Spinal JNK signaling pathway is involved in the development and maintenance of incisional pain in rats. Key words: Pain, postoperative; JNK mitogen-activated protein kinases; Spinal cord