Analgesic effects of intrathecal dexamethasone injection on chronic dorsal root ganglion compression 4nduced pain in mouse

Objective To investigate the analgesic effects of intrathecal dexamethasone injection on pain induced by chronic comDression of dorsal root ganglion in mouse.Methods The test model(CCD group)and sham model(sham group)of chronic dorsal root ganglion compression were established.Pain ethology indexes such as paw withdrawal mechanical threshold (PWMT)and Daw withdrawal thermal latency(PWTL)were assessed on 3 d before and 3 d,4d,7d.10 d,13 d,14d and 15 d after operation.The mice in group CCD were subdivided randomly into solventia group(C group),early treatment group(ET grouP),later treatment group(LT group)and twice treatment group(TT group).Vehicle(10%DMSO) and dexamethasone were intrathecally iniected at both 3 and 13 postoperative day in groups sham.C and group TT,respectively.Dexamethasone and vehicle were injected at 3 and 13 postoperative day,respectively in group ET.Vehicle and dexamethasone were injected at 3 and 13 postoperative day,respectively in group LT.Results Compared to group sham and preoperative level,PWMT and PWTL decreased at 3 postoperative day in group C(P<0.05).Intrathecal dexamethasone injection significantly increased PWMT and PWTL(P<O.05)in both groups ET and TT,however with no obvious change in pain ethology indexes in group LT.Conclusion Intrathecal dexamethasone injection alleviates pain behavior induced by chronic dorsal root ganglion compression in mouse in a time dependence manner. Key words: Glucocortieoid; Neuropathic pain; Spinal cord