Molecular analysis of excitatory amino acid receptor expression in the cochlea.

Our present understanding of excitatory neurotransmission has expanded enormously in the last decade through the use of molecular biology. In the mammalian cochlea, the analysis of excitatory amino acid receptor expression by the reverse transcription-polymease chain reaction (RT-PCR), in situ hybridization and immunochemistry has provided considerable evidence for glutamate as the afferent neurotransmitter. Using these molecular techniques, the ionotropic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), kainate, N-methyl-D-aspartic acid (NMDA) and delta receptor subunits and the metabotropic glutamate receptors have all been detected in the cochlea, in either the spiral ganglion neurons, the hair cells or both. Due to the utility of the techniques and the diversity of expressed neurotransmitter receptors, molecular biology will continue to provide important information for researchers of the auditory periphery.