Unitary ototoxic gentamicin exposure may not disrupt the function of cochlear outer hair cells in mice

Background: Previous study showed that mild ototoxic exposure could induce a reversible hearing impairment, and the loss and secondary incomplete recovery of cochlear ribbon synapses could be responsible for the hearing loss. However, it remains unclear whether cochlear outer hair cells’ (OHCs) functions are affected.

Objective: To verify whether the function of OHCs are also affected significantly after the ototoxic exposure.

Methods: Mice were injected intraperitoneally with 100?mg/kg concentration of gentamicin daily for 14 days. Distortion Product of Oto-acoustic Emission (DPOAE) was detected at control (pre-treatment), Day 0, day 4, day 7, day 14 and day 28 after the ototoxic exposure, respectively. In addition, the morphology of OHCs was observed by electron microscopy, OHCs has been counted by light microscopy, and the hearing thresholds were detected by auditory brain response (ABR).

Results: No significant changes have been found in OHC and OHC stereocilia among the experimental groups (p?>?.05). Further, no significant changes or loss was found in the morphology of OHCs either. However, we found ABR threshold elevations occurred after ototoxic exposure.

Conclusions: Unitary ototoxic gentamicin exposure may not disrupt the function of cochlear OHCs in mice, regardless of hearing loss identified in this ototoxic exposure.