Vitamins C and E modulate neuronal potassium currents.

We investigated the effects of vitamins C and E on the delayed-rectifier potassium current (IK(DR)), which is important in repolarizing the membrane potential, and on the transient A-type potassium current (IK(A)), which regulates neuronal firing frequency. The whole-cell patch-clamp technique was used to measure the currents from cultured Drosophila neurons derived from embryonic neuroblasts. The membrane potential was stepped to different voltages between -40 and +60 mV from a holding potential of -80 mV. IK(DR) and IK(A) measured in the vitamin C-containing solution (IK(DR) 305 +/- 16 pA, IK(A) 11 +/- 2 pA) were smaller than those measured in the control solution (488 +/- 21 pA, IK(A )28 +/- 3 pA). By contrast, IK(DR) and IK(A) measured in the vitamin E-containing solution (IK(DR) 561 +/- 21 pA, IK(A )31 +/- 3 pA) were greater than those measured in the control solution (422 +/- 15 pA, 17 +/- 2 pA). These results indicate that vitamins C and E can modulate potassium current amplitudes and possibly lead to altered neuronal excitability.