The Mechanisms of Post-Tetanic Potentiation in Cat Soleus and Gastrocnemius Muscles

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Abstract
Post-tetanic potentiation of muscle contraction strenght (PTP) occurs in cat soleus and gastrocnemius muscles. However, the mechanisms of potentiation are different in these two muscles. Soleus PTP is predominantly a neural event. The application of a high frequency stimulus to the soleus nerve regularly causes each subsequent response to a single stumulus to become repetitive. This post-tetanic repetitive activity (PTR) originates in the motor nerve terminal and is transmitted to the muscle. Consequently each potentiated seleus contraction is a brief tetanus. In gastrocnemuius PTR occurs too infrequently to account for PTP. Furthermore. PTP occurs in curarized directly stimulated gastrocnemius muscles to the same extent as in the indirectly stimulated muscle. In this instance PTP is a muscle phenomenon.