[Long-term gentamicin ototoxicity in the rat: research on retro-cochlear involvement by study of evoked auditory potentials of the brain stem].

Four groups of rats treated with single (50 mg/kg and 200 mg/kg) or multiple (3 X 200 mg/kg and 5 X 200 mg/kg) doses of gentamycin were studied over a 6-month period and compared with a control group. At 50 mg/kg no significant changes were observed. Significant signs of intoxication were observed at 200 mg/kg doses and at multiple doses. A significant lengthening of the latencies with changes in amplitude and a transitional increase in the auditory threshold were observed as early as the end of treatment. This was followed by a phase of amplitude decrease, a rise in auditory threshold and a decrease in latencies which remains unexplained.