Kanamycin induced low-frequency hearing loss in the budgerigar (M e l o p s i t t a c u s u n d u l a t u s)

Abstract

The chronic effects of kanamycin (KM) on hearing in the budgerigar were investigated by behavioral audiometry. The birds received a daily intramuscular injection of KM (100 mg/kg or 200 mg/kg) for 10 successive days, and absolute thresholds between pre‐ and post‐treatment were compared. KM induced both transient and permanent low‐frequency specific hearing loss; i.e., the elevation of threshold for frequencies below 1 kHz was greater than that for frequencies above 1 kHz. Moreover, the degree of hearing loss was dose dependent. The low‐frequency selective effects of KM in the present study were contrary to the high‐frequency specificity of aminoglycoside ototoxicity in mammals. To assess the effect of KM on auditory frequency resolution, critical ratios were estimated in pathological birds with low‐frequency specific hearing loss. There was a linear relation between shift in critical ratio and shift in absolute threshold, suggesting that the increase in the critical ratio is due to a decrease in the efficiency of the detector mechanism rather than a change in the spectral resolving power of the birds.