title: Muscarinic receptor M3 mediates human gallbladder contraction through voltage-gated Ca2+ channels and Rho kinase.
abstract: OBJECTIVE
  Muscarinic receptors mediate contraction of the human gallbladder through unclear receptor subtypes. The aim of the present study was to characterize muscarinic acetylcholine receptors mediating contraction of the human gallbladder.
  
  
  METHODS
  Contraction of human gallbladder muscle strips caused by agonists carbachol and muscarine was measured and the inhibition of carbachol-induced contraction by muscarinic receptor antagonists was evaluated. Reverse transcription polymerase chain reaction was performed to determine the existence of muscarinic receptor subtypes.
  
  
  RESULTS
  Carbachol and muscarine caused concentration-dependent contraction of gallbladder strips. Four receptor antagonists, including atropine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), methoctramine, and pirenzepine, inhibited the carbachol-induced contraction. The relative inhibitory potency of these receptor antagonists was atropine > 4-DAMP > methoctramine > pirenzepine. The antagonist affinity estimates (pA(2) values) correlated with the known affinities at M(3), M(4), and M(5) muscarinic receptors. In addition, the M(4)-selective antagonist muscarinic toxin 3 did not inhibit and the M(5)-selective positive allosteric modulator VU0238429 did not potentiate carbachol-induced gallbladder contraction. This suggests that M(3) muscarinic receptors mediate the muscarinic response predominantly. The contractile response of carbachol was attenuated by the voltage-gated Ca(2+) channel inhibitor nifedipine and Rho-kinase inhibitor H-1152, but not affected by protein kinase C inhibitor chelerythrine. This implies the involvement of voltage-gated Ca(2+) channel and Rho kinase but not protein kinase C.
  
  
  CONCLUSIONS
  These results suggest a major role of M(3) muscarinic receptors mediating the human gallbladder contraction through voltage-gated Ca(2+) channels and Rho kinase. M(3)-selective muscarinic receptor antagonists could be of therapeutic importance in the treatment of biliary motility disorders.
authors.affiliation: Department of Surgery, Buddhist Tzu Chi General Hospital, Hualien, and Tzu Chi University, Hualien, Taiwan.
authors.forename: Ming-Che
authors.initials: MC
authors.lastname: Lee
authors.forename: Ying-Chin
authors.initials: YC
authors.lastname: Yang
authors.forename: Yen-Cheng
authors.initials: YC
authors.lastname: Chen
authors.forename: Shih-Che
authors.initials: SC
authors.lastname: Huang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015220:Calcium Channels / Q000378:metabolism*; D005260:Female; D005704:Gallbladder / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000378:metabolism / Q000502:physiology*; D043587:Receptor, Muscarinic M3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D043588:Receptor, Muscarinic M4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D043642:Receptor, Muscarinic M5 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D043587:Receptor, Muscarinic M3; D043588:Receptor, Muscarinic M4; D043642:Receptor, Muscarinic M5; D054460:rho-Associated Kinases