Exp Mol Med.
2003 Feb;35(1):46-52.
Five subtypes of muscarinic receptors are expressed in gastric smooth muscles of guinea pig
- Affiliations
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- 1Department of Physiology, College of Medicine, Seoul National University, Seoul 110-799, Korea.
- 2Department of Biophysics, College of Medicine, Seoul National University, Seoul 110-799, Korea.
- 3Department of Physiology, Sungkyunkwan Medical School, Suwon 440-746, Korea.
- 4Clinical Research Institute, Seoul National University Hospital, Seoul 110-460, Korea.
- 5Department of Biochemistry, College of Medicine, Seoul National University, Seoul 110-799, Korea.
- 6Department of Molecular Biology/Aging, College of Medicine, Seoul National University, Seoul 110-799, Korea.
- 7Apoptosis Research Center (AARC) College of Medicine, Seoul National University, Seoul 110-799, Korea.
Abstract
- Muscarinic receptors play key roles in the control of gastrointestinal smooth muscle activity. However, specific physiological functions of each subtype remain to be determined. In this study, the nonselective cation channel activated by carbachol (ICCh) was examined in circular smooth muscle cells of the guinea pig gastric antrum using patch-clamp technique. 4-DAMP inhibited ICCh dose- dependently with IC50 of 1.1 +/- 0.1 nM (n = 6). GTPgS- induced current, however, was not inhibited by 10 nM 4-DAMP. ICCh was not recorded in pertussis- toxin (PTX)-pretreated smooth muscle cells of gastric antrum. ICCh values in response to 10 mM CCh at a holding potential of 60 mV were -330 32 pA (n=4) and -15 +/- 3 pA (n = 6) in the control and PTX-treated cells, respectively (P<0.01). Sensitivities to nanomolar 4-DAMP and PTX suggest the possible involvement of m4 subtype. Using sequence information obtained from cloned guinea pig muscarinic receptor genes, it is possible to amplify the cDNAs encoding m1-m5 from guinea pig brain tissue. Single cell RT-PCR experiments showed that all five subtypes of muscarinic receptor were present in circular smooth muscle cells of the guinea pig gastric antrum. Together with our previous results showing that Go protein is important for activation of ACh-activated NSC channels, our results suggest that ICCh might be activated by acetylcholine through m4 subtype as well as m2 and m3 subtypes in guinea-pig stomach.
Keyword
MeSH Terms
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Animals
Base Sequence
Carbachol/pharmacology
Cations
Cholinergic Agonists/pharmacology
Dose-Response Relationship, Drug
Drug Interactions
Guinea Pigs
Ion Channels/drug effects/metabolism/physiology
Muscarinic Antagonists/pharmacology
Muscle Contraction/drug effects
Muscle, Smooth/drug effects/*metabolism
Piperidines/pharmacology
Receptors, Muscarinic/chemistry/classification/*metabolism
Stomach/drug effects/*metabolism
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