Specific Gq protein involvement in muscarinic M3 receptor-induced phosphatidylinositol hydrolysis and Ca2+ release in mouse duodenal myocytes

Br J Pharmacol. 1997 Jun;121(3):451-8. doi: 10.1038/sj.bjp.0701157.


1. Cytosolic Ca2+ concentration ([Ca2+]i) during exposure to acetylcholine or caffeine was measured in mouse duodenal myocytes loaded with fura-2. Acetylcholine evoked a transient increase in [Ca2+]i followed by a sustained rise which was rapidly terminated after drug removal. Although L-type Ca2+ currents participated in the global Ca2+ response induced by acetylcholine, the initial peak in [Ca2+]i was mainly due to release of Ca2+ from intracellular stores. 2. Atropine, 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, a muscarinic M3 antagonist), pirenzepine (a muscarinic M1 antagonist), methoctramine and gallamine (muscarinic M2 antagonists) inhibited the acetylcholine-induced Ca2+ release, with a high affinity for 4-DAMP and atropine and a low affinity for the other antagonists. Selective protection of muscarinic M2 receptors with methoctramine during 4-DAMP mustard alkylation of muscarinic M3 receptors provided no evidence for muscarinic M2 receptor-activated [Ca2+]i increase. 3. Acetylcholine-induced Ca2+ release was blocked by intracellular dialysis with a patch pipette containing either heparin or an anti-phosphatidylinositol antibody and by external application of U73122 (a phospholipase C inhibitor). 4. Acetylcholine-induced Ca2+ release was insensitive to external pretreatment with pertussis toxin, but concentration-dependently inhibited by intracellular dialysis with a patch pipette solution containing an anti-alpha q/alpha 11 antibody. An antisense oligonucleotide approach revealed that only the Gq protein was involved in acetylcholine-induced Ca2+ release. 5. Intracellular applications of either an anti-beta com antibody or a peptide corresponding to the G beta gamma binding domain of the beta-adrenoceptor kinase 1 had no effect on acetylcholine-induced Ca2+ release. 6. Our results show that, in mouse duodenal myocytes, acetylcholine-induced release of Ca2+ from intracellular stores is mediated through activation of muscarinic M3 receptors which couple with a Gq protein to activate a phosphatidylinositol-specific phospholipase C.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Caffeine / pharmacology
  • Calcium / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / physiology
  • Duodenum / metabolism*
  • GTP-Binding Proteins / physiology*
  • Heparin / pharmacology
  • Hydrolysis
  • Mice
  • Muscle, Smooth / metabolism*
  • Pertussis Toxin
  • Phosphatidylinositols / metabolism*
  • Receptor, Muscarinic M3
  • Receptors, Muscarinic / physiology*
  • Type C Phospholipases / physiology
  • Virulence Factors, Bordetella / pharmacology
  • beta-Adrenergic Receptor Kinases


  • Phosphatidylinositols
  • Receptor, Muscarinic M3
  • Receptors, Muscarinic
  • Virulence Factors, Bordetella
  • Caffeine
  • Heparin
  • Pertussis Toxin
  • Cyclic AMP-Dependent Protein Kinases
  • beta-Adrenergic Receptor Kinases
  • Type C Phospholipases
  • GTP-Binding Proteins
  • Acetylcholine
  • Calcium