Antinociceptive action of sodium valproate in the mouse.

The antinociceptive action of sodium valproate (VPA) was examined using male NMRI mice. Using the hot-plate assay at 60 degrees C, orally-administered VPA (50-400 mg/kg) produced antinociceptive effects; the ED50 was about 160 mg/kg. Oral doses of VPA (6.3-400 mg/kg) decreased the writhing response elicited by intraperitoneally-injected acetic acid. The antinociceptive effect of VPA, as determined with the writhing test, exhibited complex characteristics, the most pronounced effect occurring at doses of 12.5-50 mg/kg. The antinociceptive effect of VPA in the writhing test was not antagonized by bicuculline or by naloxone. VPA, like other agents which enhance central GABA-ergic mechanisms, might possess analgesic activity.