Hair cells, the mechanotransducers of the inner ears and lateral lines of vertebrates offer an excellent preparation for the study of presynaptic mechanisms at fast chemical synapses. They offer the compact, almost cylindrical shape of an epithelial cell without entangling dendrites and axons, and make afferent synapses directly from the cell body. The biology of hair cells demands an unusually high performance of the output synapse, requiring continuous, and very quickly modulated transmitter exocytosis. Release follows the small receptor potential generated by the transduction apparatus; more transmitter is released upon depolarization, less after hyperpolarization. In some hair cells, transmission can phase-lock to kilohertz stimulus frequencies, preserving temporal information across the synapse.

We have exploited the synaptic terminal-like features of these cells to explore both the physiology and ultrastructure of the machinery underlying neurotransmitter release.