Effect of intrathecal minocycline on expression of CD 55protein in spinal cord dorsal horn in rats with neuropathic pain

Objective To investigate the effect of intrathecal minocycline on expression of CD55 protein in spinal cord dorsal horn in rats with neuropathic pain.The aim of this study is to seek the mechanism of NPP.Methods Forty-eight male SD rats weighing 200-250g in which intrathecal(IT) catheter was successfully implanted without complication were randomly divided into 4groups(n= 12):group sham operation(group A),group chronic constriction injury(group B),group solvent control(group C)and group minocycline(group D).Neuropathic pain was produced by chronic constriction nerve injury in group B,group C and group D.50μg minocycline was injected IT once a day for 7consecutive days in group D,while in group C,the equal volume of normal saline was given instead.Mechanical pain threshold and thermal pain threshold were measured before(baseline)and on the 1st,3rd and 7th day after operation.The rats were then put down and L4-L6lumbar spinal tissues were removed for examination of protein expression of CD55 by Western blot and immunohistochemistry.Results Compared with T0,TWL and MWT were decreased significantly at T1-T3(P0.05).Compared with group A,TWL at T2,T3and MWT at T1-T3 were significantly decreased and the protein expression of CD55down-regulated in group B,group C and group D(P 0.05).Compared with group D,TWL at T2,T3and MWT at T1-T3 were significantly decreased and the protein expression of CD55down-regulated in groups B and C(P0.05).Conclusion CD55 protein increased by intrathecal minocycline in spinal cord dorsal horn,CD55protein may play a key role on formation of neuropathic pain.