AIM: To investigate the effect and the possible mechanism of ginsenoside Rb1 on small intestinal smooth muscle motility in mice. METHODS: Intestinal smooth muscle strips were isolated from male ICR mice (5 wk old), and the effect of ginsenoside Rb1 on spontaneous contraction was recorded with an electrophysiolograph. The effect of ginsenoside Rb1 on ion channel currents, including the voltage-gated K+ channel current (IKv), calcium-activated potassium channel currents (IKCa), spontaneous transient outward currents and ATP-sensitive potassium channel current (IKATP), was recorded on freshly isolated single cells using the whole-cell patch clamp technique. RESULTS: Ginsenoside Rb1 dose-dependently inhibited the spontaneous contraction of intestinal smooth muscle by 21.15% +/- 3.31%, 42.03% +/- 8.23% and 67.23% +/- 5.63% at concentrations of 25 mu mol/L, 50 mu mol/L and 100 mu mol/L, respectively (n = 5, P < 0.05). The inhibitory effect of ginsenoside Rb1 on spontaneous contraction was significantly but incompletely blocked by 10 mmol/L tetraethylammonium or 0.5 mmol/L 4-aminopyridine, respectively (n = 5, P < 0.05). However, the inhibitory effect of ginsenoside Rb1 on spontaneous contraction was not affected by 10 mu mol/L glibenclamide or 0.4 mu mol/L tetrodotoxin. At the cell level, ginsenoside Rb1 increased outward potassium currents, and IKV was enhanced from 1137.71 +/- 171.62 pA to 1449.73 +/- 162.39 pA by 50 mu mol/L Rb1 at +60 mV (n = 6, P < 0.05). Ginsenoside Rb1 increased IKCa and enhanced the amplitudes of spontaneous transient outward currents from 582.77 +/- 179.09 mV to 788.12 +/- 278.34 mV (n = 5, P < 0.05). However, ginsenoside Rb1 (50 mu mol/L) had no significant effect on IKATP (n = 3, P < 0.05). CONCLUSION: These results suggest that ginsenoside Rb1 has an inhibitory effect on the spontaneous contraction of mouse intestinal smooth muscle mediated by the activation of IKV and IKCa, but the KATP channel was not involved in this effect. (C) 2012 Baishideng. All rights reserved.