Figure 1. C57BL/6J mice as the animal model of AHL. (A) Elevation in auditory brainstem response thresholds was observed in aging C57BL/6J mice (n = 45) at click, 8, 16, and 32 kHz. (B) H&E histology shows the development of cochlear structures and pathology as age increased. *P < 0.05 compared to control; scale bars of 200 μm (left panel) and 50 μm (right panel). (C) Nerve fiber density in habenular openings at mid-basal turn in six-week-old and one-year-old B6 mice (scale bar = 50 μm).