The properties of carbachol-activated nonselective cation channels at the single channel level in guinea pig gastric myocytes

T. M. Kang, Y. C. Kim, J. H. Sim, J. C. Rhee, S. J. Kim, D. Y. Uhm, I. So, K. W. Kim

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Abstract

We investigated the properties of carbachol (CCh)-activated nonselective cation channels (NSCCCh) 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 dependent 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 NSCHCCh by modulating both the open state probability and the unitary conductance, and there is one binding site for the extracellular cations within the pore.

Original languageEnglish
Pages (from-to)291-298
Number of pages8
JournalJapanese Journal of Pharmacology
Volume85
Issue number3
DOIs
StatePublished - 24 Apr 2001

Keywords

  • Carbachol
  • Gastric smooth muscle
  • Nonselective cation channel
  • Single channel

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