What the cochlea does next : encoding sound at the cochlear inner hair cell synapse

Abstract

The development of new techniques for studying synaptic interactions between nerve cells have affected the way in which we think about the synapses of the inner ear. The synapse of the inner hair cell is the first relay on the pathway through from the cochlea to the brain, and any disorders of its working present as a neuropathy. This short review summarizes some of the relevant background to understand the design of new experiments to uncover the working of this synapse. Using imaging methods the ribbon synapse of the inner hair cell can be studied in semi-intact systems of the organ of Corti. Exploiting a unique property of the cell biology of hair cells, the fluorescent membrane dye FM1-43 can be trafficked down to label synaptic vesicles at the basolateral end of the cell. The experiments identify functional properties of the hair cell ribbon synapse, where the neurotransmitter is packaged in vesicles and released rapidly and over long periods with relatively little fatigue. The technique may also clarify the roles of two new auditory neuropathy genes, pejvakin and otoferlin.