| Research Abstract |
Various neurotransmitters and thier receptors distributed in the inner ear were examined using both immunocytochemical and molecular biological tequniques. The present study mainly focused on glutamate, which is thought to be a hair cell transmitter. With regard to glutamate receptors, the cellular localization of NMDA and AMPA type glutamate receptor subunits was studied within the rodent (rat, guinea pig) and nonhuman primate (monkey) inner ear. In the spiral and vestibular ganglion, slmost all cells were immunoreactive for the NMDARI subunit and the AMPA type receptor subunit GluR2/3,4. 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. At the ultrastructural level, GluR2/3,4 are localized on the post-synaptic membrane apposed to the hair cells. In addition, the distribution of the other neurotransmitter candidates including aspartate, GABA,taurine, and substance P,were immunocytochemically examined. Involvement of GABA gamma receptor in the ganglion cells was suggested.
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