Objective: To determine the in vitro effect of Radix Saposhnikoviae (RS)

Largehead Atractylodes Rh (LA) and white paeony root (WPR) on the colonic smooth muscle strips of rats and study the possible mechanisms. Method: The colonic longitudinal smooth muscle strips of rats were prepared. Sodium chloride (9 g ·L-1) was used as the control groups. We observed the effects of WPR

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

we also observed the effects of three tool drugs (naloxone

propranolol and phentolamine) on the strips. Result: Compared with the control group

both LA and WPR had the promoting role on the in vitro contraction of colonic smooth muscle strips. In addition

the activity of LA was stronger than WPR. RS of different concentrations showed dose-dependent inhibitive effects on 10~40 g ·L-1 in the spontaneous contraction of colonic muscle strips. When acetylcholine was Added

RS showed dose-dependent inhibitive effects on the contraction of muscle strips. 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 in vitro contraction of colonic smooth muscle strips of rats

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.