title: Acetylcholine evokes an InsP3R1-dependent transient Ca2+ signal in rat duodenum myocytes.
abstract: In smooth muscle myocytes, agonist-activated release of calcium ions (Ca2+) stored in the sarcoplasmic reticulum (SR) occurs via different but overlapping transduction pathways. Hence, to fully study how SR Ca2+ channels are activated, the simultaneous activation of different Ca2+ signals should be separated. In rat duodenum myocytes, we have previously characterized that acetylcholine (ACh) induces Ca2+ oscillations by binding to its M2 muscarinic receptor and activating the ryanodine receptor subtype 2. Here, we show that ACh simultaneously evokes a Ca2+ signal dependent on activation of inositol 1,4,5-trisphosphate (InsP3) receptor subtype 1. A pharmacologic approach, the use of antisense oligonucleotides directed against InsP3R1, and the expression of a specific biosensor derived from green-fluorescent protein coupled to the pleckstrin homology domain of phospholipase C, suggested that the InsP3R1-dependent Ca2+ signal is transient and due to a transient synthesis of InsP3 via M3 muscarinic receptor. Moreover, we suggest that both M2 and M3 signalling pathways are modulating phosphatidylinositol 4,5-bisphosphate and InsP3 concentration, thus describing closely interacting pathways activated by ACh in duodenum myocytes.
authors.affiliation: Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Fritz
authors.forename: Fabrice
authors.initials: F
authors.lastname: Dabertrand
authors.forename: Jean
authors.initials: J
authors.lastname: Mironneau
authors.forename: Nathalie
authors.initials: N
authors.lastname: Macrez
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Morel