Specific G(q) protein involvement in muscarinic M3 receptor-induced phosphatidylinositol hydrolysis and Ca2+ release in mouse duodenal myocytes

J. L. Morel, N. Macrez, J. Mironneau
British Journal of Pharmacology. 1997-05-01; 121(3): 451-458
DOI: 10.1038/sj.bjp.0701157

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1. Br J Pharmacol. 1997 Jun;121(3):451-8.

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

Morel JL(1), Macrez N, Mironneau J.

Author information:
(1)Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, CNRS ESA
5017, Université de Bordeaux II, France.

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.

DOI: 10.1038/sj.bjp.0701157
PMCID: PMC1564711
PMID: 9179386 [Indexed for MEDLINE]

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