Effects of paeoniflorin on the formalin-induced nociceptive behaviour in mice

In this study, we attempted to identify the mechanisms of paeoniflorin on a ntinociceptive effects in mice. Paeoniflorin (48, 96, 240, 480 mug, i.c.v.) showed dose-related antinociception both on the early and late phases of f ormalin test in mice. Moreover, paeoniflorin (48 mug, i.c.v.) could potenti ate the antinociception of morphrine (0.5, 1.0 mg/kg, s.c.) in the formalin test. However, the antinociceptive effects of paeoniflorin were not potent iated by L-arginine (600 mg/kg, i.p.) or antagonized by beta -funaltrexamin e (beta -FNA) (10 mug, i.c.v.), ICI-174,864 (1 mug, i.c.v.) and ryanodine ( 10 ng, i.c.v.) on both the early and late phases of formalin test. L-NAME ( 75 mg/kg, i.p.) could reverse the effect of paeoniflorin on the late phase of formalin test. Naloxone (1 mg/kg, i.p.) and nor-binaltorphimine (nor-BNI ) (1 mug, i.c.v.) could block the paeoniflorin-induced antinociception on t he early phase of formalin test. These results suggested that the central a ntinociceptive effects of paeoniflorin on formalin test in mice were mediat ed by the activation of kappa -opioid receptor and not related to the incre ase of intracellular calcium. (C) 2001 Elsevier Science Ireland Ltd. All ri ghts reserved.