[Mechanism of trace hyperpolarization of the action potential of snail giant neurons].

Depolarization current decreases and hyperpolarization current increases the amplitude of tracing hyperpolarization of the neuron action potential. Calcium-defficient solution supresses the tracing depolarization, and turns the rhythmical activity of the neuron into the flashlike one. An increase of outer concentration of potassium ions decreases the tracing depolarization. The latter is suppressed completely when the membrane behaves as a potassium electrode. The suppressing effect of the increase of potassium outer concentration on tracing hyperpolarization decreases with a decrease of calcium ions content in the medium. When an active release of sodium ions from the cell is inhibited with DNP and substitution of sodium ions by lithium ions the tracing hyperpolarization of the action potential is suppressed. The tracing hyperpolarization is also suppressed during the shunting of the electrogenic effect of potassium pump with the outcoming current of chlorine ions. It is suggested that the tracing hyperpolarization of the single action potential is due to the calcium-dependent fraction of electrogenic release of sodium ions from the cell.