A study of the end-plate potential in sodium deficient solution.

1. The effect of anticholinesterases in lengthening the end-plate potential is much more pronounced in a low-sodium solution than in an ordinary Ringer-curare solution.2. To investigate this difference, intracellular recordings of end-plate potentials and of end-plate currents in voltage-clamped muscle fibres were used.3. It was found that the very large lengthening of the end-plate potential in a low-sodium solution was due to a combination of three factors: (i) lengthening of the underlying end-plate current, (ii) an increased membrane resistance and (iii) marked inward-going (anomalous) rectification of the muscle membrane.