Single Na+ channel currents observed in cultured rat muscle cells.
The voltage- and time-dependent conductance of membrane Na+ channels is responsible for the propagation of action potentials in nerve and muscle cells. In voltage-step-clamp experiments on neurone preparations containing 10(4)-10(7) Na+ channels the membrane conductance shows smooth variations in time, but analysis of fluctuations and other eivdence suggest that the underlying single-channel conductance changes are stochastic, rapid transitions between 'closed' and 'open' states as seen in other channel types. We report here the first observations of currents through individual Na+ channels under physiological conditions using an improved version of the extracellular patch-clamp technique on cultured rat muscle cells. Our observations support earlier inferences about channel gating and show a single-channel conductance of approximately 18 pS.
D000818:Animals; D002478:Cells, Cultured; D004553:Electric Conductivity; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials; D008839:Microelectrodes / Q000295:instrumentation; D009132:Muscles / Q000502:physiology*; D051381:Rats; D012964:Sodium / Q000502:physiology*
D007473:Ion Channels; D012964:Sodium