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, 50μL 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 final 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 frequency of the gallbladder muscle strip in 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, a receptor, H1 receptor, Ca2+ channel, but not related to prostaglandin.
