RESUMO
To observe the expression of cyclooxygenase (COX)-1 and COX-2 in brain after spared nerve injury (SNI) and compare the analgesic effects of COX inhibitors with different selectivity. Radioimmunoassay, RT-PCR and Western blotting techniques were used to evaluate the change of brain COX expression at different time points( before SNI, 1 h, 12 h, 1 d, 3 d, 7 d, 14 d, 30 d and 60 d after SNI); By exploring hot plate test, we observed the reacting time of animals after injection of saline, NS-398, SC-560 and indomethacin at different time points. The results showed that: ( 1 ) The expression of brain COX-1 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 ( all P ＜0.05 ); (2) NS-398 showed significant analgesic effect on neuropathic pain after SNI at the early phase ( P ＜ 0.05 ), but didn't persist for over 30 d; ( 3 ) Indomethacin and SC-560 didn't show significant analgesic effects until 14 d. These results suggest that 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.