[Cooperative effect of calcium ions in freeing a mediator from the neuromuscular synapses of large and small muscle fibers of frog sartorius muscle].

The dependence of a amplitude and quantum content (m) of the end plate potentials on the external calcium concentration was studied in experiments on the frog sartorius amplitude of the miniature end plate potentials were found. The data obtained suggest that the number of calcium ions taking part in the release of each transmitter quantum may be different.