Glutamate is the afferent neurotransmitter in the human cochlea

Glutamate, the most important afferent neurotransmitter in the auditory sys tem, is thought to be the afferent transmitter between the cochlear inner h air cells and afferent neurons, hitherto visualized only in the cochlea of animal species. It has been identified for the first time in sections from the human inner ear, L-glutamate, NMDAR2B and the enzyme glutamine syntheta se were identified by using monoclonal antibodies. The distribution pattern of the transmitter L-glutamate in the human cochlea is similar to that obs erved in other mammals. L-glutamate was identified adjacent to outer and in ner hail cells and in the spiral ganglion. Similar distributions were found for glutamine synthetase and the ionotropic NMDA receptor subunit NMDAR2. The identification of neurotransmitters and their receptors in the human co chlea has implications for the pharmacotherapy of inner ear diseases.