THE EFFECTS OF LITHIUM ON THE NEUROMUSCULAR JUNCTION OF THE FROG

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Abstract
The effects of lithium on the end-plate potential [e.p.p.], miniature end-plate potential and their post-tetanic potentiation were studied at the neuromuscular junction of the frog. Lithium decreased the amplitude of end-plate potential to 85% in curarized muscle and to 55% in the Mg-blocked muscle. Lithium reduced the size of miniature end-plate potentials to about 80%. This should be ascribed to the effects of lithium on the post-synaptlc events. In the Mg-treated muscle the quantum contents of e.p.p. were smaller in the lithium solution than in the normal solution, indicating that lithium has also a pre-synaptic action. When the muscle was tetanized in the lithium solution, the so-called post-tetanic potentiation of e.p.p. disappeared, and the amplitude of e.p.p. was greatly reduced. The potentiation of the frequency of miniature end-plate potential could be seen, but the increase of the frequency did not return to pre-tetanic level.