AIM: To observe the effect of Fructus Psoraleae on motility of isolated gallbladder muscle strips of guinea pigs and its mechanism.METHODS: Guinea pigs were hit to lose consciousness and the whole gallbladder was removed quickly. Two or three smooth muscle strips (8 mm × 3 mm) were cut along a longitudinal direction. The mucosa was gently removed. Every longitudinal muscle strip was suspended in a tissue chamber which was continuously perfused with 5 mL Krebs solution (37℃), pH 7.4, and aerated with 950 mL/L O2 and 50 mL/L CO2. The isometric response was recorded with an ink-writing recorder. After 2 h equilibration under 1 g-load, 50 μL Fructus Psoraleae (10, 20, 70, 200, 700, 1000 g/L) was added cumulatively into the tissue chamber in turn every 2 min to observe their effects on gallbladder muscle strips (cumulating fihal concentration of Fructus Psoraleae was 0.1, 0.3, 1.0,3.0, 10.0, 20.0 g/L). The antagonists, including 4-DAMP,benzhydramine, hexamethonium, phentolamine, verapamil and idomethine were given 2 min before Fructus Psoraleae respectively to investigate the mechanisms involved.RESULTS: Fructus Psoraleae dose-dependently increased the resting tension (r = 0.992, P ＜ 0.001), decreased the mean contractile amplitude (r = 0.970, P ＜ 0.001) and meanwhile increased the contractile fiequency of the gallbladder muscle stripin vitro (r = 0.965,P ＜ 0.001). The exciting action of Fructus Psoraleae on the resting tension could be partially blocked by 4-DAMP (the resting tension decreased from 1.37 + 0.41 to 0.70± 0.35, P ＜ 0.001), benzhydramine (from 1.37 ± 0.41 to 0.45 ± 0.38, P ＜ 0.001), hexamethonium (from 1.37 ± 0.41 to 0.94 ± 0.23, P ＜ 0.05), phentolamine ( from 1.37± 0.41 to 0.89 ± 0.22, P ＜ 0.01) and verapamil (from 1.37± 0.41 to 0.94 ± 0.26, P ＜ 0.05). But the above antagonists had no significant effect on the action of Fructus Psoraleae-induced mean contractile amplitude (P ＞ 0.05).Moreover, the increase of the contractile frequency due to Fructus Psoraleae was inhibited by 4-DAMP (decreased from 8.3 ± 1.2 to 6.8 + 0.5, P ＜ 0.01) and hexamethonium (from 8.3 ± 1.2 to 7.0 + 0.9, P ＜ 0.05). Idomethine had no significant effect on the Fructus Psoraleaeinduced responses (P ＞ 0.05).CONCLUSION: Fructus Psoraleae enhances the motility of isolated gallbladder muscle strips from guinea pigs, in a dose-dependent manner. The effect of Fructus Psoraleae is partly related to M3, N receptor, α receptor, H1receptor, Ca2+ channel, but not related to prostaglandin.