Antinociceptive effects of the traditional Chinese (Kampo) medicines, Hochu-ekki-to, Yoku-kan-san and Saiko-ka-ryukotsu-borei-to, were studied on acetic acid-induced writhing in mice. The number of writhings observed was counted in consecutive 5 min periods for 60 min after intraperitoneal injection of 0.6% acetic acid. Kampo medicines were administered for 14 consecutive days, prior to testing, in the drinking water. Oral administration of Hochu-ekki-to (60, 150 and 300 mg/kg/day) dose-dependently reduced the number of acetic acid-induced writhings. Yoku-kan-san (60, 150 and 300mg/kg/day) tended to inhibit the writhing response to acetic acid in a dose-related manner. Saiko-ka-ryukotsu-borei-to (60, 150 and 300 mg/kg/day) markedly reduced the number of acetic acid-induced writhings but its effects were not dose-dependent. These results suggest that these Kampo medicines may have antinociceptive properties.
