Mobilization of Transmitter by Hyperpolarization

RECENT investigations have shown that repetitive stimulation produces hyperpolarization of nerve terminals 1,2 . It has been suggested that such a hyperpolarization could account for post-activation potentiation, since the height of the action potential in the pre-synaptic terminals would be increased, and this in turn might enhance synaptic transmission 3 . Evidence which seemed to support this concept was obtained by Castillo and Katz 4 , who showed that at the frog neuromuscular junction the size of the end-plate potential may be increased by extrinsic currents which hyperpolarize the nerve endings.