Phenobarbital increases spontaneous transmitter release at the frog neuromuscular junction

Phenobarbital (1-2 × 10(-4)M) markedly increases the frequency of miniature end-plate potentials at the neuromuscular synapse of the frog. This effect was seen in calcium free media containing EGTA. The drug probably acts presynaptically at an intracellular locus to increase the presynaptic free calcium concentration.