Glutathione accelerates sodium channel inactivation in excised rat axonal membrane patches

The effects of glutathione were studied on the gating behaviour of
sodium channels in membrane patches of rat axons. Depolarizing
pulses from –120 to –40 mV elicited sodium currents of up to 500
pA, indicating the simultaneous activation of up to 250 sodium
channels. Inactivation of these channels in the excised, inside-out
configuration was fitted by two time constants ( h1=0.81 ms; h2=
5.03 ms) and open time histograms at 0 mV revealed a biexponential
distribution of channel openings ( short=0.28 ms; long=3.68 ms).
Both, the slow time constant of inactivation and the long lasting
single channel openings disappeared after addition of the reducing
agent glutathione (2–5 mM) to the bathing solution. Sodium channels
of excised patches with glutathione present on the cytoplasmatic
face of the membrane had inactivation kinetics similar to channels
recorded in the cell-attached configuration. These observations
indicate that redox processes may contribute to the gating of
axonal sodium channels.