Barbiturate-induced transmitter release at a frog neuromuscular junction.

1. The influence of barbiturates on neuromuscular transmission at end-plates of frog sartorius muscles was investigated electrophysiologically on preparations bathed in Ringer solution containing a low concentration of calcium and a high concentration of magnesium.2. Effects of a convulsant barbiturate, 5-(2-cyclohexylideneëthyl)-5-ethyl barbituric acid (CHEB), were compared with those of phenobarbitone.3. CHEB and phenobarbitone increased the mean quantum content of the end-plate potentials and decreased the mean amplitude of the miniature end-plate potentials.4. Both barbiturates enhanced the duration of the nerve-terminal action potential and had little or no effect on the effective resistance of the skeletal muscle membrane.