Role of JNK signaling pathway in dexmedetomidine-induced reduction of spinal neurotoxicity induced by lidocaine in rats / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the role of C-Jun N-Terminal kinase (JNK) signaling pathway in dexmedetomidine-induced reduction of spinal neurotoxicity induced by lidocaine in rats.Methods Seventy-two adult male Sprague-Dawley rats, weighing 280-320 g, in which intrathecal catheters were successfully implanted without complications, were randomly divided into 6 groups (n =12 each) using a random number table control group (group C);SP600125 (JNK signaling pathway blocker) group (group SP);dexmedetomidine group (group D);lidocaine group (group L);dexmedetomidine + lidocaine group (group DL);SP600125+lidocaine group (group SPL).Dimethyl sulfoxide (DMSO) 20 μl was injected intrathecally in group C.SP600125 30 μg and 10％ lidocaine 20 μl were injected intrathecally in SP and L groups, respectively.At 20 min after intrathecal injection of 10％ lidocaine, dexmedetomidine 75 μg/kg was injected intraperitoneally in group DL, and SP600125 30 μg was injected intrathecally in group SPL.Dexmedetomidine 75 μg/kg was injected intraperitoneally in group D.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured before intrathecal catheters were implanted (T0), before intrathecal administration (T1), and at 4, 8 and 12 h and 1, 2, 3, 4, 5 and 6 days after intrathecal administration (T2-10).At 24 h after intrathecal administration, 6 rats randomly selected from each group were sacrificed.The lumbar segment (L4-5) of the spinal cord was removed for detection of cell apoptosis (by TUNEL) and phosphorylated JNK (p-JNK) expression (by Western blot).The apoptotic index was calculated.Results Compared with group C, no significant change was found in the MWT, TWL, apoptotic index and expression of p-JNK in SP and D groups (P＞0.05), the MWT at T2-8 in group L, at T2-6 in group DL and at T2-5 in group SPL were significantly increased, the TWL at T2-8 in group L, at T2-5 in group DL and at T2-4 in group SPL were prolonged, and the apoptotic index and expression of p-JNK were increased in DL, SPL and L groups (P＜0.05).Compared with group L, the MWT was significantly decreased, and the TWL was shortened at T2-8, and the apoptotic index and expression of p-JNK were decreased in DL and SPL groups (P＜0.05).Conclusion The mechanism by which dexmedetomidine mitigates spinal neurotoxicity induced by lidocaine is related to inhibited activation of JNK signaling pathway in rats.