title: Functional roles of muscarinic M2 and M3 receptors in mouse stomach motility: studies with muscarinic receptor knockout mice.
abstract: Functional roles of muscarinic acetylcholine receptors in the regulation of mouse stomach motility were examined using mice genetically lacking muscarinic M(2) receptor and/or M(3) receptor and their corresponding wild-type (WT) mice. Single application of carbachol (1 nM-30 microM) produced concentration-dependent contraction in antral and fundus strips from muscarinic M(2) receptor knockout (M(2)R-KO) and M(3) receptor knockout (M(3)R-KO) mice but not in those from M(2) and M(3) receptors double knockout (M(2)/M(3)R-KO) mice. A comparison of the concentration-response curves with those for WT mice showed a significant decrease in the negative logarithm of EC(50) (pEC(50)) value (M(2)R-KO) or amplitude of maximum contraction (M(3)R-KO) in the muscarinic receptor-deficient mice. The tonic phase of carbachol-induced contraction was decreased in gastric strips from M(3)R-KO mice. Antagonistic affinity for 4-diphenylacetoxy-N-methyl-piperidine (4-DAMP) or 11-([2-[(diethylamino)methyl]-1-piperdinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one (AF-DX116) indicated that the contractile responses in M(2)R-KO and M(3)R-KO mice were mediated by muscarinic M(3) and M(2) receptors, respectively. Electrical field stimulation (EFS, 0.5-32 Hz) elicited frequency-dependent contraction in physostigmine- and N(omega)-nitro-L-arginine methylester (l-NAME)-treated fundic and antral strips from M(2)R-KO and M(3)R-KO mice, but the cholinergic contractile components decreased significantly compared with those in WT mice. In gastric strips from M(2)/M(3)R-KO mice, cholinergic contractions elicited by EFS were not observed but atropine-resistant contractions were more conspicuous than those in gastric strips from WT mice. Gastric emptying in WT mice and that in M(2)/M(3)R-KO mice were comparable, suggesting that motor function of the stomach in the KO mice did not differ from that in the WT mice. The results indicate that both muscarinic M(2) and M(3) receptors but not other subtypes mediate carbachol- or EFS-induced contraction in the mouse stomach but that the contribution of each receptor to concentration-response relationships is distinguishable. Although there was impairment of nerve-mediated cholinergic responses in the stomach of KO mice, gastric emptying in KO mice was the same as that in WT mice probably due to the compensatory enhancement of the non-cholinergic contraction pathway.
authors.affiliation: Department of Pharmacology, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan. tko-kita@rakuno.ac.jp
authors.forename: Takio
authors.initials: T
authors.lastname: Kitazawa
authors.forename: Kano
authors.initials: K
authors.lastname: Hashiba
authors.forename: Jinshan
authors.initials: J
authors.lastname: Cao
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Unno
authors.forename: Sei-Ichi
authors.initials: S
authors.lastname: Komori
authors.forename: Masahisa
authors.initials: M
authors.lastname: Yamada
authors.forename: Jürgen
authors.initials: J
authors.lastname: Wess
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Taneike
mesh_terms: D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005746:Gastric Emptying / Q000187:drug effects / Q000502:physiology; D005748:Gastric Fundus / Q000187:drug effects / Q000502:physiology; D005838:Genotype; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D010890:Pirenzepine / Q000031:analogs & derivatives / Q000494:pharmacology; D043585:Receptor, Muscarinic M2 / Q000235:genetics / Q000502:physiology*; D043587:Receptor, Muscarinic M3 / Q000235:genetics / Q000502:physiology*; D013270:Stomach / Q000187:drug effects / Q000502:physiology*
chemical_list: D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D018727:Muscarinic Antagonists; D010880:Piperidines; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D010890:Pirenzepine; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D002217:Carbachol; D010830:Physostigmine; C048593:otenzepad; D019331:NG-Nitroarginine Methyl Ester