Quantal nature of transmission at the synapse between hair cells and eighth nerve fibers.

1. An intracellular recording technique was used to record excitatory postsynaptic potentials (EPSP's) from the eighth nerve fibers of goldfish. EPSP's were evoked by applying sound stimulus, and spontaneous miniature EPSP's were also observed. 2. Even when the stimulus sound was kept at a fixed intensity level, the EPSP amplitude showed some fluctuations including occasional failures of the response. 3. The applicability of Poisson's law was tested for several intensity levels of sound stimulus in the same fibers. The Poisson relation was found applicable to the amplitude distribution of EPSP's evoked by a weak sound, but some discrepancies were found for a strong sound. 4. It was concluded that the transmission between hair cells and primary eighth nerve fibers of goldfish occurred in quantal steps. Some theoretical implications of the present results were discussed.