title: Simo decoction promotes contraction of antral circular smooth muscle mainly via muscarinic M3 receptor.
abstract: BACKGROUND
  Simo Decoction (SMD), a traditional Chinese medicine, included four elements, such as Fructus aurantii, Radix aucklandiae, Semen arecae and Radix linderae. It has been used to improve gastrointestinal dysmotility in clinical practice for a long history in China. However, the explicit mechanisms are unclear. The aim of this study was to investigate the effect of SMD on contractions of antral circular smooth muscle strips of Sprague-Dawley (SD) rats and its underlying mechanism.
  
  
  METHODS
  The antral circular strips were prepared in the organ bath under baseline or to be incubated with muscarinic receptor antagonist atropine (10(-6)M), muscarinic M3 receptor antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) (0.4×10(-6)M), muscarinic M2 receptor antagonist gallamine (10(-6)M), adrenergic receptor agonist adrenaline (10(-7)M), exogenous nitric oxide (NO) donor l-arginine (10(-4)M), nicotinic receptor antagonist hexamethonium chloride (10(-4)M) and Ca(2+) channel antagonist nifedipine (30nM), and consecutive concentrations of SMD were added to the bath to observe the strip responses. As a control, the responses of strips after administration with the same volume of Krebs solution as SMD were also noted. The strip responses to acetylcholine (10(-7)-10(-3)M) were also noted in organ bath to compare with SMD-induced contraction.
  
  
  RESULTS
  SMD dose-dependently evoked hypercontractility of antral circular strips, and the maximal contractile effect of circular smooth muscle induced by SMD was significantly higher than that induced by acetylcholine (10(-3)M). The responses of antral circular strips to SMD were completely antagonized by atropine, 4-DAMP or 4-DAMP+gallamine, but partly inhibited by gallamine and partly suppressed by adrenaline, l-arginine, hexamethonium chloride and nifedipine.
  
  
  CONCLUSIONS
  SMD promotes contractions of antral circular strips in rats mainly via activation of muscarinic M3 receptor, but partly via activation of muscarinic M2 receptor, Ca(2+) channel and nicotinic receptor, inhibition of adrenergic receptor and releasing of NO.
authors.affiliation: Division of Gastroenterology, Union Hospital of Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Road, Wuhan, China. dchibing@126.com.
authors.forename: Chibing
authors.initials: C
authors.lastname: Dai
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.forename: Wenmei
authors.initials: W
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Qian
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Hou
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000502:physiology; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology; D011706:Pyloric Antrum / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043585:Receptor, Muscarinic M2 / Q000502:physiology; D043587:Receptor, Muscarinic M3 / Q000502:physiology*; D011941:Receptors, Adrenergic / Q000502:physiology; D011978:Receptors, Nicotinic / Q000502:physiology
chemical_list: D015220:Calcium Channels; D004365:Drugs, Chinese Herbal; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D011941:Receptors, Adrenergic; D011978:Receptors, Nicotinic; C542832:simo; D009569:Nitric Oxide