Development of aminoglycoside induced hearing loss in cats

Behaviorally trained cats [J. L. Orr, D. B. Moody. and W. C. Stebbins, J. Acoust. Soc. Am. 62, 1268–1272 (1977)] were tested with a threshold tracking procedure. Subcutaneous 60 mg/kg/day injections of kanamycin (Mcat. Fcat. and Ycat) or amikacin (Gcat) were given until a threshold shift of at least 20 dB occurred at 8 kHz. The hearing loss occurred first at 45 kHz and then progressed to 32, 16, and 8 kHz. Mcat, Fcat, and Gcat had similar cytocochleograms. No hair cells remained for several mm in the basal turn. For a few mm only inner hair cells were present, and then both inner and outer hair cells were present. These cats had normal low frequency hearing, threshold shifts (67 dB at 8 kHz for Mcat: 34 dB at 4 kHz for Fcat; 17 dB at 4 kHz and 59 dB at 8 kHz for Gcat), and no hearing at higher frequencies. Ycat had normal hearing to 8 kHz, no hearing at higher frequencies and cytocochleograms with a sharp transition from present to missing hair cells.