RESUMEN
AIM: To compare the expression of three cyclooxygenase (COX) isoforms in the process of inflammatory pain and evaluate the analgesic effects of different protocols about usage of COX inhibitors on inflammatory pain. METHODS: Formalin was injected subplantarly to mice to induce inflammatory pain. The expression of COX-1, COX-2 and COX-3 was evaluated by radioimmunoassay and RT-PCR, respectively. For the analgesic effect assay, animals were divided into 5 groups including control, SC, NS, IN and NS + SC group. The former 4 spectively. In the NS + SC group, animals received NS398 during the first 1 month and SC-560 during the second month in the NS + SC group. RESULTS: The expression of COX-1 was higher at the late phase while that of COX-2 was higher at the early phase of inflammatory pain. The expression of COX-3 did not significantly change in the process of inflammatory pain. Additionally,behavioral assessment showed that using COX-2 inhibitors at the early phase followed by COX-1 inhibitors at the late phase could get better analgesic effect on inflammatory pain compared with single using COX-1 selective or COX-2 selective inhibitors. CONCLUSION: In brain, the expression of COX-2 increases rapidly in the inflammatory pain process while COX-1 expression does not increase till the late phase. Brain COX-3 is poorly involved in the inflammatory process. Combined use of COX-1 and COX-2 selective inhibitors may be a better protocol in inflammatory pain treatment.