ABSTRACT
Objective To evaluate the role of MCP/DAF expression in the spinal cord in the development of neuropathic pain (NP) induced by chronic constrictive injury (CCI) of the sciatic nerve in rats.Methods Twenty-four Sprague-Dawley rats transfected with MCP/DAF,weighing 200-250 g,were randomly divided into 2 groups (n =12 each) using a random number table:sham operation of transfected rat group (Rsham group) and CCI of transfected rat group (RCCI group).Twenty-four healthy male Sprague-Dawley rats,weighing 200-250 g,were randomly divided into 2 groups (n =12 each) using a random number table:sham operation of normal rat group (Nsham group) and CCI of normal rat group (NCCI group).The right sciatic nerve was exposed and 4 loose ligatures wen placed on the sciatic nerve at 1 mm intervals with 4-0 catgut in RCCI and NCCI groups.The right sciatic nerve was only exposed in Rsham and Nsham groups.Paw withdrawal threshold to yon Frey filament stimulation (PWT) and paw withdrawal latency to nociceptive thermal stimulation (PWL) were measured at 1 day before operation (baseline) and 1,3 and 7 days after operation.The animals were sacrificed after measurement of pain threshold on 7 days after operation and the L4,5 segment of the spinal cord was removed for determination of the expression of OX-42 (by immuno-histochemistry) and MCP mRNA and DAF mRNA (by RT-PCR).Results Compared with Nsham group,the PWT and PWL were significantly decreased on 1,3 and 7 days after operation,the expression of OX-42 was up-regulated,and the expression of MCP mRNA and DAF mRNA was down-regulated in NCCI group (P ＜ 0.05),and no significant changes were found in the PWT and PWL on 1,3 and 7 days after operation and expression of OX-42(P ＞ 0.05),and the expression of MCP mRNA and DAF mRNA was up-regulated in Rsham and RCCI groups (P ＞ 0.05).Compared with NCCI group,the PWT and PWL were significantly increased on 1,3 and 7 days after operation,the expression of OX-42 was down-regulated,and the expression of MCP mRNA and DAF mRNA was up-regulated in RCCI group (P ＜ 0.05).Conclusion Up-regulation of MCP/ DAF expression in the spinal cord can inhibit the development of NP in rats and regulation of activation of microglias in the spinal cord is involved in the mechanism.