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Pflügers Archiv

, Volume 382, Issue 2, pp 127–132 | Cite as

Effect of repetitive stimulation on the frog neuromuscular transmission

  • Fabio Ruzzier
  • Maria Scuka
Excitable Tissues and Central Nervous Physiology

Abstract

Presynaptic and postsynaptic effects on the neuromuscular transmission were studied during 20 min of indirect stimulation at 10/s. During the ‘facilitation’ period, there was an increase in the quantal content, in the frequency of miniature endplate potentials and in their amplitude. All these parameters were decreased during the ‘depression’ period. Besides, the end-plate current (e.p.c.), recorded during this high rate of stimulation, increasingly lengthened. The falling phase of the e.p.c. was exponential during facilitation, while marked deviations from the exponential time course were observed during depression. The experiments showed that a possible change in the kinetics between the receptors and the mediator was not responsible for the lengthened time course of the e.p.c. Therefore, it is assumed that either the delayed diffusion of the transmitter from the synaptic cleft or an altered mechanism of the release of acetylcholine may be involved. The latter possibility is supported by a progressive prolongation of the synaptic delay, which was observed during a prolonged repetitive stimulation.

Key words

Frog neuromuscular junction Repetitive stimulation Facilitation Quantal content Endplate current 

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Copyright information

© Springer-Verlag 1979

Authors and Affiliations

  • Fabio Ruzzier
    • 1
  • Maria Scuka
    • 1
  1. 1.Institute of Physiology, Medical FacultyUniversity of TriesteTriesteItaly

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