The efferent medial olivocochlear-hair cell synapse

Amplification of incoming sounds in the inner ear is modulated by an efferent pathway which travels back from the brain all the way to the cochlea. The medial olivocochlear system makes synaptic contacts with hair cells, where the neurotransmitter acetylcholine is released. Synaptic transmission is mediated by a unique nicotinic cholinergic receptor composed of α9 and α10 subunits, which is highly Ca2+ permeable and is coupled to a Ca2+-activated SK potassium channel. Thus, hyperpolarization of hair cells follows efferent fiber activation. In this work we review the literature that has enlightened our knowledge concerning the intimacies of this synapse.

► We provide a review of the properties of the efferent olivocochlear-hair cell synapse.
► Activation of efferent fibers leads to hyperpolarization of hair cells.
► This is brought about by the activation of an atypical nicotinic receptor.
► This receptor is highly calcium permeable.
► Calcium activates a calcium-dependant SK potassium channel.