THE EFFECT OF CÆSIUM IONS ON NEUROMUSCULAR TRANSMISSION IN THE FROG

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Abstract
The effect of Cs+ on neuromuscutlar transmission in the frog has been investigated. In both K+‐containing and K+‐free solutions, the presence of Cs+ allowed a gradual increase in the amplitude of the evoked end‐plate potential (e.p.p.) which was due to an increase in the output of transmitter. However, after prolonged exposure to Cs+ in K+‐free solutions, the duration of the e.p.p. was increased and its amplitude progressively reduced, eventually to zero. The effects of Cs+ were reversible. The results are consistent with the idea that exposure to Cs+ ions allows their entry into nerve terminals in exchange for K+ ions, thereby resulting in an increased duration of the projunctional action potential.