title: Site of action of the general anesthetic propofol in muscarinic M1 receptor-mediated signal transduction.
abstract: Although a potential target site of general anesthetics is primarily the GABA A receptor, a chloride ion channel, a previous study suggested that the intravenous general anesthetic propofol attenuates the M1 muscarinic acetylcholine receptor (M1 receptor)-mediated signal transduction. In the present study, we examined the target site of propofol in M1 receptor-mediated signal transduction. Two-electrode voltage-clamp method was used in Xenopus oocytes expressing both M1 receptors and associated G protein alpha subunits (Gqalpha). Propofol inhibited M1 receptor-mediated signal transduction in a dose-dependent manner (IC50 = 50 nM). Injection of guanosine 5'-3-O-(thio)triphosphate (GTPgammaS) into oocytes overexpressing Gqalpha was used to investigate direct effects of propofol on G protein coupled with the M1 receptor. Propofol did not affect activation of Gqalpha-mediated signal transduction with the intracellular injection of GTPgammaS. We also studied effects of propofol on l-[N-methyl-3H]scopolamine methyl chloride ([3H]NMS) binding and M1 receptor-mediated signal transduction in mammalian cells expressing M1 receptor. Propofol inhibited the M1 receptor-mediated signal transduction but did not inhibit binding of [3H]NMS. Effects of propofol on Gs- and Gi/o-coupled signal transduction were investigated, using oocytes expressing the beta2 adrenoceptor (beta2 receptor)/cystic fibrosis transmembrane conductance regulator or oocytes expressing the M2 muscarinic acetylcholine receptor (M2 receptor)/Kir3.1 (a member of G protein-gated inwardly rectifying K(+) channels). Neither beta2 receptor-mediated nor M2 receptor-mediated signal transduction was inhibited by a relatively high concentration of propofol (50 microM). These results indicate that propofol inhibits M1 receptor-mediated signal transduction by selectively disrupting interaction between the receptor and associated G protein.
authors.affiliation: Department of Pharmacology, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Murasaki
authors.forename: Muneshige
authors.initials: M
authors.lastname: Kaibara
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nagase
authors.forename: Sayaka
authors.initials: S
authors.lastname: Mitarai
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Doi
authors.forename: Koji
authors.initials: K
authors.lastname: Sumikawa
authors.forename: Kohtaro
authors.initials: K
authors.lastname: Taniyama
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D004594:Electrophysiology; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D019832:N-Methylscopolamine / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D010276:Parasympatholytics / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D015742:Propofol / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D043643:Receptor, Muscarinic M1 / Q000187:drug effects* / Q000378:metabolism; D043585:Receptor, Muscarinic M2 / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014982:Xenopus laevis
chemical_list: D018686:Anesthetics, Intravenous; C505032:CFTR protein, human; D018076:DNA, Complementary; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D010276:Parasympatholytics; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D043643:Receptor, Muscarinic M1; D043585:Receptor, Muscarinic M2; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019205:GTP-Binding Protein alpha Subunits, Gs; D000109:Acetylcholine; D019832:N-Methylscopolamine; D015742:Propofol