Key role of external chloride ions in regulation of fast sodium channels in rat cerebellum Purkinje neurons.

A decrease in the external chloride ion concentration to 4 mM caused a decrease in the fast sodium current to 85-100% in rat cerebellum Purkinje neurons in the whole-cell configuration using the patchclamp method. This effect did not depend on the main cation from the internal side of the cell membrane (120 mM of potassium or cesium) and also appeared when Cl- was substituted with sulfate (SO2-4) or phosphate (H2PO4-) anion outside of the cell. The effect was reversible after washing out the low chloride by the standard saline.