Effects of Aminoglycoside Antibiotics on the Auditory Brainstem Response and Post Rotatory Nystagmus in Rats

Effects of three aminoglycoside antibiotics, amikacin (AMIK),tobramycin (TOB), and gentamicin (GM), on the auditory and vestibularfunctions were assessed in rats, the most frequently used speciesin toxicity studies. Chronic electrodes for auditory brainstemresponse (ABR) recording were implanted on the epidural surface,and those for post rotatory nystagmus (PRN) were implanted atthe nictitating membrane and the outer canthus. AMK, TOB, andGM were given intramuscularly twice daily for 3–4 weeksat a daily dose of 350, 150, and 100 mg/kg, respectively. Theamplitude of each wave of the ABR was decreased or disappearedin the groups treated with AMK, TOB, and GM. In the PRN, theduration of the nystagmus was decreased in the TOB group andcompletely lost in the GM group. No abnormality was observedin the PRN in the AMK group. These results were similar to thosereported in the ototoxicity studies of these drugs in guineapigs and indicate that ototoxicity can be evaluated in ratsas successfully as in guinea pigs by this procedure.