The origin of hyperpolarization based on the directional conduction of action potential using a model nerve cell system.

ABSTRACT

In nerve cells, changes in local membrane potentials are generated and propagated along a nerve axon mainly by the function of K+ and Na+ channels. Generally, concurrent monitoring of multi-points on an axon is performed based on the voltage-clamp method. As the respective membrane potentials have been evaluated by considering the relations between the applied potential, the local current, and conductance, experimental values are not directly evaluated. We directly measured the actual membrane potentials and local currents of the respective cells using a nerve-model system comprising liquid-membrane cells. It was then proven that the action potential spreads along the axon toward the axon terminal due to the function of both the channel-type receptors in the synapse and voltage-gated Na+ channels on the axon, and that hyperpolarization cannot be caused by only the operation of the delayed-K+ and the voltage-gated Na+ channels.