Expression of potassium-chloride co-transporter in spinal cord dorsal horn after peripheral nerve injury

Objective To investigate the expression of potassium-chloride co-transporter(KCC2)in spinal cord dorsal horn in rat model of neuropathic pain induced by spared nerve injury (SNI).Methods Twenty-seven adult male SD rats,weighing 200-250 g,were randomly divided into 2 groups:SNI group (n=18);sham-operation group (n=9).In the SNI group,the left sciatic nerve of rats and its trifurcations were exposed,and their tibial and common peroneal nerves were tightly ligated and cut distally,while preserving the sural nerve intact.In sham-operated animals,the left sciatic nerve was exposed but not transected.The mechanical withdrawal threshold (MWT) to von Frey filaments was measured 1d before operation and 1 d,3 d,5 d,7 d,14 d,and 21 d post-operation.The animals were sacrificed at 1,3,5,and 7 d after SNI and the lumbar segment of the spinal cord were removed.The expression of KCC2 in the spinal cord dorsal horn (L4,L5) was determined by Western blotting analysis.Results The MWT of the ipsilateral paws in SNI group decreased to (3.23±0.49),(0.60±0.09),(0.38±0.07) and (0.21±0.06) g on day 1,3,5,and 7 d after operation,respectively,and then remained unchanged for 21 days after operation.On day 1,3,and 5 d after operation,KCC2 expression in the left spinal cord dorsal horn in the SNI group was significantly lower than that of the right sides (0.97±0.09 vs.0.53±0.15,0.32±0.10 vs.0.63±0.09 and 1.27±0.08 vs.1.11±0.18,all P0.05).On day 3 after operation the expression in the right side was 0.63±0.09,which was significantly lower than that of the sham-operation group (P0.05).Conclusion Our results indicate that peripheral nerve injury can induce down-regulation of KCC2 in the dorsal horn of the spinal cord in rats,which may contribute to the development of chronic neuropathic pain.(Shanghai Med J,2010,33:312-315)