Changes in the avian cochlea after single high-dose gentamicin.

Area of Science:

• Ototoxicity research
• Inner ear biology
• Auditory neuroscience

Background:

• Gentamicin is an aminoglycoside antibiotic with known ototoxic effects.
• Understanding the time course of hair cell damage and recovery is crucial for developing therapeutic strategies.
• The chicken inner ear provides a valuable model for studying hair cell regeneration.

Purpose of the Study:

• To define the time course of functional and anatomical damage to hair cells in the chicken inner ear following a single high dose of gentamicin.
• To investigate the subsequent recovery and regeneration of these hair cells.
• To correlate functional changes (auditory brainstem response) with anatomical damage (scanning electron microscopy).

Main Methods:

• Broiler chicks received a single intraperitoneal dose of gentamicin (200 mg/kg) or saline.
• Auditory brainstem response (ABR) thresholds were measured at multiple time points post-injection.
• Cochleae were examined using scanning electron microscopy (SEM) to assess hair cell damage and numbers.

Main Results:

• Significant variability in both ABR thresholds and SEM findings was observed among animals.
• Maximal damage occurred at 5 days post-injection, with an average ABR threshold shift of 12 dB and 28% basal cochlear damage.
• Hair cell regeneration led to rapid anatomical and functional recovery, though disorganization persisted at 70 days.

Conclusions:

• A single high dose of gentamicin induces substantial, albeit variable, anatomical and functional damage in the chick cochlea.
• Hair cell regeneration facilitates a rapid but incomplete recovery process.
• The findings highlight the complex interplay between gentamicin-induced ototoxicity and the regenerative capacity of the inner ear.