Changes in expression of protein kinase Cγand Cαin dorsal horn of spinal cord in rat with neuropathic pain

Objective To investigate the changes in the expression of protein kinase Cγand Cα(PKCγ, PKCα) in the dorsal horn of spinal cord in a rat with neuropathic pain. Methods Twenty-four healthy SD rats weighing 150-250 g were randomly divided into 3 groups (n = 8 each): groupⅠsham operation; groupⅡchronic constructive injury (CCI) and groupⅢspinal nerve ligation (SNL) . CCI was produced by placing 4 loose ligatures on the sciatic nerve at 1 mm intervals with 4-0 catgut and SNL by ligation and transaction of L5 spinal nerve. The threshold to von Frey hair stimulation and radiant heat were measured before operation (baseline) and on the 2nd, 4th and 7th day after operation. The animals were killed after measurement of pain threshold. The lumbar segment (L4-6) of the spinal cord was removed for determination of the expression of PKCγ, PKCαand Fos protein by immuno-histochemistry. Results The mechanical and thermal withdrawal latencies were significantly decreased on the 4th and 7th day after operation as compared to the baselines values before operation in CCI and SNL groups. But there was no significant difference in the withdrawal latencies to mechanical and thermal stimuli between CCI and SNL groups. The expression of PKCγ, PKCαand Fos protein was significantly higher in CCI and SNL groups than in sham operation group. The expression of PKCαand Fos protein was not significantly different between CCI and SNL groups, while PKCγexpression was significantly higher in group SNL than in group CCI.Conclusion The increase in the expression of PKCγand PKCαin the dorsal horn of spinal cord is involved in the mechanism of central sensitization in the neuropathic pain.