Change of COX-1/2 expression in brain after SNI induced neuropathic pain

Aim To observe the expression of cyclooxygenase COX-1 and 2 in brain after spared nerve injury(SNI).Methods Pain thresholds by hot-plate test were determined before,1 h,12 h,1d,3 d,7 d,14 d,30 d and 60 d after SNI.Three methods were used to evaluate the change of brain COX expressionafter SNI,radioimmunoassay for measurement of PGF_(1α)(catalyzed by COX-1)and PGE_2(catalyzed by COX-2),RT-PCR for mRNA and Western blotting for protein.Time points for assay were before SNI,1 h,12 h,1 d,3 d,7 d,14 d,30 d and 60 d after SNI.Results Pain thresholds of mice decreased significantly during the period of 60 d after SNI(all P0.05).The concentration of PGF_(1α) in brain increased significantly at 14 d after SNI while the increase of PGE_2 concentration appeared at 3 d after SNI(all P0.05).The levels of brain COX-1 mRNA and protein didn′t increase significantly until 14 d after SNI,while that of COX-2 increased significantly and rapidly after SNI and reached peak at the time point of 1 d.Conclusion Brain COX-1 is involved in the late phase of neuropathic pain and may play a role in the persistence of pain,while brain COX-2 is involved in the early phase of neuropathic pain and may play a role in the pain origination.