Aim To determine the effect of Radix Saposhnikoviae (RS)

Largehead Atractylodes Rh (LA) and White Paeony Root (WPR) on the colonic smooth muscle strips from rats in vitro and study the possible mechanisms. Methods The colonic longitudinal smooth muscle strips of rats were prepared. Sodium chloride (9g/L) was used as the control groups. We observed the effects of WPR

LA and RS on the spontaneous contraction in muscle strips. To further study its mechanisms

we also observed its effects on the strips fully influenced by three medicines (Naloxone

Propranolol and Phentolamine) in advance. Result Compared with the NS group

both LA and WPR had the promoting role on the contraction of colonic smooth muscle strips of rats in vitro. What’s more

the activity of LA was stronger than WPR. RS of different concentrations showed dose-dependent inhibitive effects on 10～40g/L in the spontaneous contraction of colonic muscle strips in vitro. Added acetylcholine

RS showed dose-dependent inhibitive effects in the contraction of muscle strips initiated by acetylcholine partly in vitro. Compared with the NS RS group

the area of NLT RS group had significant difference (P<0.05)

so were the peak and area of FTLM RS group (P<0.01)

while NS group was insignificant. Conclusion RS showed inhibitive effect on the spontaneous contraction of colonic smooth muscle strips of rats in vitro

while LA and WPR showed promoting effect. The mechanisms of inhibition are supposed to have close relations with the α-adrenoceptor and maybe also related with the M-cholinergic receptor.