Flunixin meglumine (FM) is a potent non-steroidal anti-inflammatory drug used in veterinary clinical practice. Hyperalgesia was induced by mtraplantar (i.pl.) administration of carrageenan (500 mu g) into the rat hind paw. Electronic von Frey apparatus was used to determine paw withdrawal threshold in grams (g). Both, FM (0.095-0.12 mg/kg: s.c.) and N-G-nitro-L-arginine methyl ester (L-NAME 2.5 and 5 mg/kg; i.p.), given 2.5 h after i.pl. injection of carrageenan produced significant dose-dependent antinociceptive effects. When FM (0.095 mg/kg) and subeffective dose of L-NAME (7.5 mg/kg) were co-administered, the anti-nociceptive effect was significantly increased M comparison with the effect of FM alone. L-arginme (10 mg/kg: i.p.) itself did not produce significant effect on carrageenan-induced hyperalgesia, but significantly inhibited the anti-nociceptive effects of both FM and FM + L-NAME combination. The inhibition of production of nitric oxide might be involved in the mechanism of the anti-hyperalgesic effect of FM in a model of carrageenan-induced hyperalgesia in rats
