Influence of the extracellular and intracellular redox state on ionic fluxes through the membranes of D-type nerve cells of Lymnea stagnalis

Abstract

1. The influence of the extracellular and intracellular redox state on ion passage through the cholinergic, voltage-dependent and leakage current channels of giant neurones of Lymnea stagnalis has been analysed with the voltage-clamp method. The following observations were made. 2. Oxidizing agents decreased and reducing agents increased the membrane potential. 3. When applied extracellularly, the oxidizing agents slightly decreased, and the reducing agents strongly decreased conductance through the cholinergic channels, while after intracellular application the reverse effects were noted. 4. The reversal potential was shifted to the right by the reductants and to the left by the oxidants after their extracellular application. 5. Intracellular application produced inversion. ΔV ACh values were increased by the extracellular oxidants and decreased by the reductants. Intracellularly only the reductant effects occurred inversely. 6. Conductance through the potassium voltage-dependent channels was increased monotonically by the increasing redox state both on extra- and intracellular application of the redox agents. The Ca 2+- Na + current showed peak-type dependence. 7. The leakage currents were increased by raising the redox state. From the above fact it follows that the giant neurone membranes—as with other membranes—have a redox-sensitive system to control ion passage through the cholonergic, voltage-dependent and leakage current channels.