The Journal of General Physiology, Vol 82, 679-701, Copyright © 1983 by The Rockefeller University Press
Sodium channel gating currents in frog skeletal muscle
DT Campbell
Charge movements similar to those attributed to the sodium channel gating
mechanism in nerve have been measured in frog skeletal muscle using the
vaseline-gap voltage-clamp technique. The time course of gating currents
elicited by moderate to strong depolarizations could be well fitted by the
sum of two exponentials. The gating charge exhibits immobilization: at a
holding potential of -90 mV the proportion of charge that returns after a
depolarizing prepulse (OFF charge) decreases with the duration of the
prepulse with a time course similar to inactivation of sodium currents
measured in the same fiber at the same potential. OFF charge movements
elicited by a return to more negative holding potentials of -120 or -150 mV
show distinct fast and slow phases. At these holding potentials the total
charge moved during both phases of the gating current is equal to the ON
charge moved during the preceding prepulse. It is suggested that the slow
component of OFF charge movement represents the slower return of charge
"immobilized" during the prepulse. A slow mechanism of charge
immobilization is also evident: the maximum charge moved for a strong
depolarization is approximately doubled by changing the holding potential
from -90 to -150 mV. Although they are larger in magnitude for a -150-mV
holding potential, the gating currents elicited by steps to a given
potential have similar kinetics whether the holding potential is -90 or
-150 mV.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
