gms | German Medical Science

Objective: The application of dexamethasone is the most effective therapy in sudden idiopathic hearing loss and induced cochlear dysfunction. However, despite its proven therapeutic effect there are some ambiguities in respect to the underlying mechanisms of the dexamethasone impact. The aim of this study was to demonstrate the influence of dexamethasone on GR-expression in different cochlear regions.

Material and methods: In total, 22 male guinea pigs were analyzed, 5 untreated control animals, 5 noise-exposed animals (90 dB, 1 h), and noise-exposed animals when 0.1ml NaCl (0.9%) was intratymanically given prior noise-exposure (n=6) or, alternatively, dexamethasone (8 mg/ml; n=6). Two hours after noise-exposure, the cochlea was removed from the bony capsule, fixated and embedded in paraffin. GR-expression was immuno histochemically quantified. Auditory brainstem responses were recorded prior noise-exposure and directly before cochlear preparation.

Results: Noise-exposure resulted in hearing loss, which was significantly lower in the dexamethasone-treated group (p<0.05). Differences in GR-expression were found comparing seven cochlear regions: organ of Corti, nerve fibers, spiral ganglion cells, fibrocytes of the limbus, stria vascularis, interdental cells, spiral ligament. The highest expression was found in the stria vascularis. Comparing the cell-specific effects of the NaCl and dexamethasone, significant differences were only identified for the spiral ligament (p<0.05) where the reduction in GR-expression was prevented by dexamethasone.

Conclusion: The application of dexamethasone in the therapy of cochlear disorders effects primarily alterations in the spiral ligament. This region has an important role in the maintenance of cochlear homeostasis.