The analgesic effect of decursinol.

Although decursinol, which is one of the coumarins purified from the dried roots of Angelica gigas Nakai, was previously demonstrated to have antinociceptive effects on various mouse pain models such as tail-flick, hot-plate, formalin, writhing, and several cytokine-induced pain tests, the possible involvement of its analgesic effects and non-steroidal anti-inflammatory drugs (NSAIDs) has not been clearly elucidated yet. In this study, we characterized the possible interaction between decursinol and aspirin or acetaminophen in the writhing test. The antinociceptive effects of decursinol were observed at an orally-administered dose of 50 mg/kg but not at 25 or 10 mg/kg. In addition, the analgesic effects of aspirin (ASA) and acetaminophen (APAP) were shown at an orally-administered dose of 200 mg/kg but not at 50 or 100 mg/kg. We examined the effects of decursinol on the ASA or APAP at sub-analgesic doses. Although the co-administration of decursinol and ASA did not show any differences at doses of 10 or 25 mg/kg and 50 or 100 mg/kg, respectively, synergistic effects between decursinol and APAP were observed in the group of decursinol (25 mg/kg) and APAP (100 mg/kg) co-administration. These results indicated that the analgesic effect of decursinol might be involved in supraspinal cyclooxygenase regulation that might be overlapped with APAP-induced analgesic mechanisms rather than systemic or peripheral prostaglandin modulation.