The effects of calcium and magnesium on statistical release parameters at the crayfish neuromuscular junction.

1. Transmitter release at excitatory neuromuscular junctions of crayfish muscle was studied at low temperature by recording synaptic potentials with extracellular micro-electrodes.2. Increasing the Ca concentration in the bathing solution produced an increase in the average number of quanta released per nerve stimulus (m). Increasing the Mg concentration resulted in a decrease in m.3. Statistical analysis of fluctuations in the quantal release from trial to trial, assuming binomial statistics, indicated that both the changes in m were due to changes in the average quantal release probability (p).