title: The properties of carbachol-activated nonselective cation channels at the single channel level in guinea pig gastric myocytes.
abstract: We investigated the properties of carbachol (CCh)-activated nonselective cation channels (NSC(CCh)) at the single channel level in the gastric myocytes of guinea pigs using a magnified whole-cell mode or an outside-out mode. The channel activity (NPo) recorded in a magnified whole-cell mode increased with depolarization (from -120 to -20 mV) and had the half activation potential of -81 mV under the symmetrical 140 mM Cs+ condition. The single channel conductance depended upon the extracellular monovalent cations with the order of Cs+ (35 pS) > Na+ (25 pS) > Li+ (21 pS). The channel activities markedly diminished or disappeared when external Cs+ was replaced with Na+ or N-methyl-D-glucamate (NMDG+). With Cs+ and Na+ as external cations, the channel showed a monotonic increase in NPo with the increased mole fraction of Cs+ over Na+, and it had an intermediate conductance value in solution containing 67% Cs+ with 33% Na+. These data suggested that the extracellular monovalent cations regulate the whole-cell current of NSC(CCh) by modulating both the open state probability and the unitary conductance, and there is one binding site for the extracellular cations within the pore.
authors.affiliation: Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea.
authors.forename: T M
authors.initials: TM
authors.lastname: Kang
authors.forename: Y C
authors.initials: YC
authors.lastname: Kim
authors.forename: J H
authors.initials: JH
authors.lastname: Sim
authors.forename: J C
authors.initials: JC
authors.lastname: Rhee
authors.forename: S J
authors.initials: SJ
authors.lastname: Kim
authors.forename: D Y
authors.initials: DY
authors.lastname: Uhm
authors.forename: I
authors.initials: I
authors.lastname: So
authors.forename: K W
authors.initials: KW
authors.lastname: Kim
mesh_terms: D000818:Animals; D002217:Carbachol / Q000494:pharmacology*; D002586:Cesium / Q000378:metabolism; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000819:agonists / Q000378:metabolism / Q000502:physiology*; D008094:Lithium / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000378:metabolism; D013270:Stomach / Q000166:cytology / Q000502:physiology*
chemical_list: D007473:Ion Channels; D002586:Cesium; D002217:Carbachol; D008094:Lithium; D012964:Sodium