Aim To observe the influences of dexmen-detomidine on the spontaneous contraction of duodenal smooth muscle of rabbits in vitro and explore the mech-anisms.Methods The rabbits ( male or female ) were stunned and the duodenums were isolated .The sam-ples of duodenal segments were connected with tension transducer , which were then put into oxygen saturation Krebs-Henseleit ( K-H) solution .The influences of dex-mendetomidine on amplitude ( AM ) and frequency ( FR ) of duodenal smooth muscle were recorded by BL-420 F biological signal processing system .The cu-mulative dosing method was used to observe the differ-ent concentrations of dexmedetomidine on duodenal smooth muscle spontaneous contraction .Glibenclamide ( Gli) was added to K-H solution before dexmendeto-midine.In the calcium-free K-H solution, calcium chloride and rynodine were added before dexmendeto-midine.The mechanisms of dexmendetomidine were studied .Results ① Dexmendetomidine reduced the amplitude of spontaneous contraction of duodenal smooth muscle in rabbits in a dose-dependent manner ( P<0.05 or P<0.01 ) , while the frequency was not obviously influenced ( P >0.05 ) .② Gli ( P <0.05 ) partly abolished the inhibitory effects of dexmendetomi-dine on duodenal smooth muscle .③ Dexmendetomi-dine inhibited the contraction of duodenum smooth muscle induced by calcium chloride ( P <0.05 ) and rynodine ( P<0.05 ) application into calcium-free K-H solution.Conclusion Dexmendetomidine inhibits the spontaneous contraction of duodenal smooth muscle of rabbits in vitro.The mechanisms may be related to ac-tivating ATP sensitive potassium channels , inhibition of the extracellular calcium influx via cell membrane and intracellular calcium release via sarcoplasmic reticulum in duodenal smooth muscle .