Fig. 1.

Topical application of gentamicin has no effect on the hearing organ. Gentamicin sulphate solution was applied directly to the round window membrane either acutely (E–H, Q) or as in a ‘slow release’ paradigm on a gelatine sponge (M–P, R). Immunofluorescence for β-III TUBULIN and the hair cell markers MYO7A (B, D, F, H) and ESPIN (J, L, N, P) show that there is no effect on the organ of Corti in either situation – comparison with untreated contralateral ears (A–D; I–L) shows no overt difference in structure or integrity of the inner and outer hair cells. Sections are counterstained with DAPI to delineate cell nuclei. There is no disruption to the innervation of the IHCs by spiral ganglion neurons (arrowheads, A, E, I, M). Click ABR measurements were taken at intervals post-treatment – no difference in response was found down to 20 dB with either treatment regime (Q, R). Arrows point to inner hair cells, brackets delineate the three rows of outer hair cells. Scale bar – 50 μm.