[Effect of changes in the external concentration of sodium, chlorine, and potassium ions on subsequent depolarization of a single node of Ranvier of isolated nerve fibers].

Change in external concentration of Na+ (from 0 to 240 mmol), Cl- (from 0 to 120 mmol), and K+ (from 2.5 to 10--30 mmol) had no significant effect on the negative trace potential in the Ranvier isthmus of Rana ridibunda. In K+-free Ringer's solution a trace hyperpolarization occurred. The negative trace potential of the isthmus increased in blockade of the membrane potassium channels with tetraethylammonium chloride or 4-aminopyrydine.