Effect of ginseng saponins on a rat visceral hypersensitivity model

The 5-hydroxytryptamine3A (5-HT3) receptor is closely related with irritable bowel syndrome (IBS) in enteric nervous systems. We previously demonstrated that ginseng total saponins (GTS, also called ginsenosides), the active ingredients of Panax ginseng, inhibit the activity of 5-HT3A receptor channels expressed in Xenopus laevis oocytes. Here, we further investigated whether the in vitro inhibitory effect of ginsenosides on 5-HT3A receptor channel activity is coupled to in vivo attenuation of IBS. A rat model of IBS was induced by colorectal distention (CRD) and intracolonic infusion of 0.6% acetic acid (CRD-acetic acid), and visceral hypersensitivity was assessed by counting the contractions in the external oblique muscles of conscious rats during the 10 min distention period. We found that oral administration of GTS significantly and dose-dependently inhibited CRD-acetic acid-induced visceral hypersensitivity. The EC50 was 5.5+/-4.7 mg/kg (95% confidence intervals: 1.2-15.7) and the inhibitory effect of GTS against visceral hypersensitivity persisted for 4 h. When we compared the effects of protopanaxadiol (PD) ginsenosides and protopanaxatriol (PT) ginsenosides against CRD-acetic acid-induced visceral hypersensitivity, we found that PT but not PD ginsenosides significantly attenuated the CRD-acetic acid-induced visceral hypersensitivity. These results indicate that PT ginsenosides of Panax ginseng might be the main active components for the attenuation of experimentally CRD-acetic acid-induced visceral hypersensitivity, and may be clinically relevant for the future treatment of IBS.