title: Signal transduction pathways of muscarinic receptors in circular smooth muscle from the rabbit caecum.
abstract: The effects of muscarinic acetylcholine receptor stimulation on phosphoinositides breakdown and adenylate cyclase activity were examined in the circular smooth muscle of the rabbit caecum. In Myo-[3H]inositol-labeled circular smooth muscle cells, carbachol caused a concentration-dependent increase in [3H]inositol phosphates ([3H]IPs) accumulation (EC50 of 3 +/- 1 microM). The M1-selective antagonist pirenzepine (PRZ), the M2-selective AF-DX 116 (11-2[[2-[(diethyl-amino)methyl]-1-piperidinyl]acetyl]-5, 11-dihydro-6Hypyrido[2,3-b][1,4]benzodiazepin-6-one) and the M3-selective para-fluoro-hexahydrosiladifenidol (p-F-HHSiD) inhibited the carbachol-induced [3H]inositol phosphates accumulation with the following order of potency; p-F-HHSiD > PRZ > AF-DX 116. In saponin-permeabilized circular smooth muscle cells, carbachol and GTP gamma [S] elicited a concentration-dependent increase in [3H]inositol phosphates accumulation. The concentration-response curve for GTP gamma [S] was shifted to the left when cells were incubated with 1 microM carbachol. The [3H]inositol phosphates accumulation elicited by simultaneous addition of 0.1 microM GTP gamma [S] and 1 microM carbachol to permeabilized cells was significantly decreased (78.28 +/- 18.23% inhibition) when cells were preincubated for 5 min with 0.1 mM GDP beta [S]. In nonpermeabilized cells, pertussis toxin did not alter the carbachol-induced increase in [3H]inositol phosphates accumulation. On the other hand, the 0.1 mM carbachol-induced inhibition of forskolin-stimulated adenylate cyclase activity in circular smooth muscle homogenates was significantly reversed by atropine and AF-DX 116, whereas PRZ and p-F-HHSiD were ineffective (muscarinic antagonists were used at 1 microM final concentration).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Laboratoire de Biochimie des Membranes, INSERM CJF 92-07, Faculté de Pharmacie, Montpellier, France.
authors.forename: P
authors.initials: P
authors.lastname: Cuq
authors.forename: R
authors.initials: R
authors.lastname: Magous
authors.forename: J P
authors.initials: JP
authors.lastname: Bali
mesh_terms: D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002432:Cecum / Q000201:enzymology / Q000378:metabolism; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009130:Muscle, Smooth / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D037342:Pertussis Toxin; D011817:Rabbits; D011976:Receptors, Muscarinic / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D010738:Type C Phospholipases / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D007295:Inositol Phosphates; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D002217:Carbachol; D000242:Cyclic AMP; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases