, Volume 326, Issue 2, pp 347-359
Date: 31 Aug 2006

Hair cell ribbon synapses

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Abstract

Hearing and balance rely on the faithful synaptic coding of mechanical input by the auditory and vestibular hair cells of the inner ear. Mechanical deflection of their stereocilia causes the opening of mechanosensitive channels, resulting in hair cell depolarization, which controls the release of glutamate at ribbon-type synapses. Hair cells have a compact shape with strong polarity. Mechanoelectrical transduction and active membrane turnover associated with stereociliar renewal dominate the apical compartment. Transmitter release occurs at several active zones along the basolateral membrane. The astonishing capability of the hair cell ribbon synapse for temporally precise and reliable sensory coding has been the subject of intense investigation over the past few years. This research has been facilitated by the excellent experimental accessibility of the hair cell. For the same reason, the hair cell serves as an important model for studying presynaptic Ca2+ signaling and stimulus-secretion coupling. In addition to common principles, hair cell synapses differ in their anatomical and functional properties among species, among the auditory and vestibular organs, and among hair cell positions within the organ. Here, we briefly review synaptic morphology and connectivity and then focus on stimulus-secretion coupling at hair cell synapses.

Research at the Moser laboratory was supported by grants from the DFG (SFB406 and CMPB), the European Commission (through the integrated project EuroHear), the Human Frontiers Science Program (HFSP), and the Federal Goverment (through the Bernstein Center for Computational Neuroscience, Göttingen). Research at the Lysakowski laboratory was supported by grants from NIH (R01 DC02521, R01 DC02290, and R01 DC002358) and the American Hearing Research Foundation.