Neurotransmitters in the cochlea and the cochlear nucleus.

The inhibitory efferent transmitter in the cochlear is most likely acetylcholine. The afferent transmitter (between hair cells and primary afferent fibres) is not known. There is some evidence for glutamate (or aspartate) but the high concentrations necessary to activate the afferents when these amino-acids are applied intracochlearly may indicate that their effects is unspecific. A number of other transmitter candidates can be safely ruled out at these synapses. In the cochlear nucleus of transmitter between primary afferents and secondary cells is probably glutamate (or aspartate).