Figure 3

Distribution of gentamicin-conjugated Texas Red (GTTR) in the inner ear after in vivo injection. (A) Postnatal day 7 Sprague-Dawley rats were injected subcutaneously with a single 300 mg kg⁻¹ dose of GTTR (b, c) or Texas Red (TR) solution (a) and then allowed to recover for 24 h. Then, the temporal bones were prepared and fixed in 4% paraformaldehyde (PFA) overnight at 4 °C. Apical and basal turns of cochlear explants were prepared and stained with fluorescein isothiocyanate (FITC)-labeled palloidin for 30 min, and specimens were observed under a fluorescent microscope. (B) The temporal bones were prepared from these rats and fixed in 4% PFA overnight at 4 °C. Next, the temporal bones were embedded in paraffin for sectioning at 4 μm thickness. The sectioned specimens were stained with FITC-labeled phalloidin for 30 min and 4′,6-diamidino-2-phenylindole (DAPI) for 10 min and examined under a fluorescent microscope. Inset shows punctuate GTTR staining observed in the cuticular plate of outer hair cells (OHCs)¹⁴ and inner hair cells (IHCs; double arrow), hair cell membrane (arrowhead), outer pillar cells (op), inner pillar cells (ip), Hensen’s cells (h) and the spiral ligament (SL).