Subsequent to conditioning by a high frequency stimulus axons of the cat soleus nerve respond to single stimuli with brief trains of repetitive action potentials. This phenomenon, post-tetanic repetitive activity (PTR), was studied in individual axons and single motor units of an in situ cat soleus nerve-muscle preparation. The occurrence, intensity, and duration of PTR are principally dependent on the frequency and duration of the conditioning tetanus. PTR occurs synchronously in the axon and muscles of single motor units. An analysis of the temporal relationships of the repetitive nerve and muscle potentials showed that PTR is generated in the motor nerve terminal. It is postulated that PTR is produced by a generator potential which is developed in the post-tetanic period between the unmyelinated nerve terminal and the last node of Ranvier.

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