Correlation between nerve terminal size and transmitter release at the neuromuscular junction of the frog

1. End-plate potentials were recorded intracellularly at the frog neuromuscular junction bathed in a solution containing a low concentration of calcium and a high concentration of magnesium. 2. The muscle was subsequently subjected to `cholinesterase staining', and the area of the individual end-plates, studied with intracellular electrodes, was measured. 3. A positive correlation was found between the end-plate area and the diameter of muscle fibres. 4. The mean quantum content ( m ) showed a positive correlation with the size of end-plates. 5. The frequency of spontaneous miniature end-plate potentials was positively correlated with m as well as with end-plate area. 6. It is concluded that the amount of transmitter released following nerve stimulation is related to the size of nerve endings.