NMDA (NMDAR1) and AMPA-type (GluR2/3) receptor subunits are expressed in the inner ear

Using receptor subunit-specific antibodies, the cellular localization of NMDA and AMPA type glutamate receptor subunits was studied within the rodent (rat, guinea pig) and non-human primate (monkey) inner ear. In the spiral and vestibular ganglion, almost all cells were immunoreactive for the NMDAR1 subunit and the AMPA type receptor subunit GluR2/3. This indicates that both NMDA and non-NMDA type glutamate receptors may be co-distributed in the primary afferent neuronal components, and are possibly involved in neurotransmission in the primary auditory and vestibular systems. This study also indicated the possible localizations of glutamate receptors in the nonneuronal cells in the inner ear, suggesting that some nonneuronal cells may also have the ability to mediate glutamate signalling.