[The generation and spread of excitation in the motor nerve ending of the frog]

Abstract

In experiments on the frog cutaneous-pectoris muscle under the visual control the evoked responses of nerve endings were recorded in proximal, central and distal parts of the terminal. At the fixed position of the recording electrode the local iontophoretic application of TTX to different terminal parts and Ranvier's nodes was performed. It was concluded, that local currents at more proximal terminal parts provide the depolarization of the located parts and conduction of excitation to the nonexcitable parts. Inward currents at behind located and already excited parts are shortened and decreased by local currents from more distal parts during the propagation of excitation. It results in shortening of the action potential and decreasing of the transmitter release in more proximal parts. This effect disappeared along the nerve terminal due to decreasing of inward Na current at the end parts.