Characterization of muscarinic receptor-mediated cationic currents in longitudinal smooth muscle cells of mouse small intestine.
In mouse intestinal smooth muscle cells held at -50 mV, carbachol evoked an atropine-sensitive inward current in the intracellular presence of Cs(+). The current response consisted of an initial peak followed by a smaller plateau component on which oscillatory currents frequently arose. Results from various experimental procedures indicated that the inward current is a muscarinic receptor-operated cationic current (mI(cat)) sensitive to cytosolic Ca(2+) concentration ([Ca(2+)](i)) and that the initial peak and oscillatory components are contaminated by Ca(2+)-activated Cl(-) currents. Under conditions of [Ca(2+)](i) buffered to 100 nM, the mI(cat) response to cumulative carbachol applications was inhibited competitively by an M(2)-selective antagonist but non-competitively by an M(3)-selective one. Also it was severely reduced by pertussis toxin (PTX) treatment or a phospholipase C (PLC) inhibitor. Comparative analysis of mI(cat) in mouse and guinea-pig intestinal myocytes indicated that the underlying channels resemble between those myocytes in agonist sensitivity, current-voltage relationship, and unitary conductance. The results suggest that in mouse intestinal myocytes, mI(cat) arises mainly via an M(2)/M(3) synergistic mechanism involving PTX-sensitive G-proteins and PLC activity in the absence of current modulation by [Ca(2+)](i) changes, as described for guinea-pig ileal mI(cat). The channels underlying mI(cat) are also indistinguishable in gating properties between both types of myocytes.
Sakamoto
Takashi
T
Department of Pathogenic Veterinary Science, United Graduate School of Veterinary Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
Unno
Toshihiro
T
Matsuyama
Hayato
H
Uchiyama
Mai
M
Hattori
Mitsunobu
M
Nishimura
Masakazu
M
Komori
Seiichi
S
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002412:Cations / Q000378:metabolism; D018679:Cholinergic Agonists / Q000494:pharmacology; D003959:Diamines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D018727:Muscarinic Antagonists / Q000494:pharmacology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D043585:Receptor, Muscarinic M2 / Q000187:drug effects / Q000378:metabolism*; D043587:Receptor, Muscarinic M3 / Q000187:drug effects / Q000378:metabolism*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D002412:Cations; D018679:Cholinergic Agonists; D003959:Diamines; D004791:Enzyme Inhibitors; D004963:Estrenes; D007473:Ion Channels; D018727:Muscarinic Antagonists; D010880:Piperidines; D011760:Pyrrolidinones; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D002217:Carbachol; D037342:Pertussis Toxin; D010738:Type C Phospholipases; C054938:methoctramine