Expression of Phosphorylated p38MAPK in Sorsal Root Ganglion in Rats with Sciatica Caused by Nucleus Pulposus

【Objective】 To observe the relationship of the expression of phosphorylated p38 mitogen activated protein kinase(p-p38MAPK) and the inflammatory reaction of dorsal root ganglion as well as sciatica caused by nucleus pulposus in rats.【Method】 Sixty-six pathogen-free adult male Sprague-Dawley rats were randomly divided into three groups: naive group(n=12) and sham group(n=18) and model group(n=36).Model group received left L5 hemilaminectomy and L5 dorsal root ganglion(DRG) epineuriumetomy as well as caudal vertebrae nucleus pulposus autograft,which establish an improved rat model of non-compressed lumbar intervertebral disc herniation.Sham groups received operation similar to model group except with muscles autograft.Naive group received no operation.50% paw withdraw threshold(50%PWT) of left hind limb was measured 1 day before the surgery and on the 1st,3rd,7th,14th and 21st day after surgery in each group by Up-Down method to detect the change of the mechanical hyperalgsia.Twelve left L5 dorsal root ganglions were collected from naive group and sham group on the 7th day after operation and model group on the 7th,14th,and 21st day after operation.Then the proportion of Cycloxygenase-2(COX-2) and p-p38MAPK positive expression cell were detected by immunohistochemistry method.【Results】 The 50% PWT showed no change after operation in sham group.The 50% PWT in the model group decreased significantly from the first day to the 21st day post-operation,The 50% PWT reached the lowest on the 14th day and partially recovered on the 21st day.The expression of COX-2 and p-p38MAPK in sham group and navie group were weak.In the 7th day,the expression of COX-2 and p-p38MAPK was significantlyhigher in model group.In the 14th day,the expression of COX-2 and p-p38MAPK continuously increased.In the 21th day modelgroup,the expression of COX-2 and p-p38MAPK significantly decreased.【Conclusion】 p-p38MAPK expression in DRG correlatedclosely with the sciatica and the inflammatory reaction caused by nucleus pulposus.