[Characteristics of the unitary end-plate potential of the frog (author's transl)]

When the transmitter release is reduced in physiological solutions with low calcium and high magnesium content (70% of transmission failure), most of the end-plate potentials are evoked by the release of one quantum. Observing a short sequence of the unitary potentials (10-30), one can see that they distribute into a few patterns of similar amplitude, latency and time to peak. The amplitude and latency frequency distributions show successions of peaks frequently set at regular intervals. The average number of peaks is 11 for the amplitude distribution and 14.5 for the latency distributions. Lowering the temperature (20-10 degrees C) lengthens the interval between the latency peaks (Q10 = 2). These observations suggest the existence of a limited number of releasing sites set at regular intervals (10-20 micrometers) along the branches of the nerve terminal. This hypothesis is discussed with regard to the well-known interpretation of the amplitude sub-units of the unitary response and the sub-miniature potentials. The time-distribution of the unitary-evoked potentials of identical latency is frequently periodic (about 60 s at 4 HZ of frequency stimulation). Slightly different frequencies can be observed at different latency values. Through our interpretation of the sub-units, these facts mean that the few active zones follow a periodic process which can explain the periodic oscillation already shown for the total activity of the neuromuscular junction.