Behavioral assessment of kanamycin-induced hearing loss in the guinea pig

Abstract

The effect of chronic kanamycin administration on absolute auditory thresholds measured with the operant conditioning procedure described in the previous paper was examined in four guinea pigs. The absolute threshold for five different frequencies was measured daily, thus permitting construction of an audiogram which ranged from 125 Hz to 34 kHz within a two-day period. Following establishment of a predrug baseline the animals received 200-mg/kg injections of kanamycin daily for 15 to 30 consecutive days. In the course of drug treatment the animals suffered permanent hearing losses which progressed gradually from the higher to the lower frequencies. The maximum threshold shift observed at any of the test frequencies was approximately 50 dB. In fact, shifts in absolute threshold at frequencies most severely affected by the drug were within a range of 35–50 dB. The correspondence between the hearing impairments determined behaviorally and the cytocochleograms constructed from light microscopic examinations of surface preparations of the organ of Corti will be discussed. [Supported by Research Grants NS05077 and NS05065 and by Program Project Grant NS05785 from NINCDS.]