The localization of subunits of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) selective glutamate receptor, termed Glutamate receptor (GluR) was examined in the rat cochlea using affinity purified polyclonal antibody to GluR subunits (GluR 1-4). GluR 2/3 and GluR 4 immunoreactive (IR) staining was observed in rat spiral ganglion cells, while GluR 1 IR was not. GluR 4 IR staining was also seen in puncta at inner and outer hair cell bases. These results suggest that GluR 2/3 and GluR 4 are components of excitatory amino acid synapses in the rat cochlea.

The purpose of this study was to determine if high intensity acoustic stimulation would induce HSP 72 in rat cochlea. The animals were exposed to 110 dB SPL broad band noise for 1.5 h and sacrificed 4, 6 and 8 h after stimulation.Immunocytochemistry and western blotting were used to detect the expression of HSP 72 in the cochlear tissues. Western blots showed an intense 72 kD band in the noise exposed animals compared to a very light band in non-stimulated control animals. Immunocytochemical results in the cochlea revealed noise induced HSP 72 immunoreactive staining of outer hair cells. Only a few immunoreactive stained inner hair cells were seen and spiral ganglion cells were not stained. These results indicate that acoustic overstimulation can induce the expression of HSP 72 in outer hair cells of the rat cochlea. HSP 72 may serve as a marker for cellular stress and potential damage and may be involved in protection from insult.

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