Normal and altered otoliths of guinea pigs. Scanning electron microscopy observations.

Normal morphology and structural alterations of the otoliths were observed in 20 young albino guinea pigs. Ten animals had been exposed to long-term treatment with an aminoglycoside antibiotic and ten others, which had not been treated, have been analyzed as a control group. The observations were carried out using scanning electron microscopy. All the animals survived the period of stabling and treatment. They were sacrificed and the temporal bones were dissected and fixed with 2% osmium tetroxide buffered at pH 7.4. The inner ear was subsequently dehydrated, microdissected, dried with CO2, and coated with gold. Different kinds of deterioration were observed and valued according to the appearance of the otoliths, which looked as if they had been melted, with many pores and wide and prominent cavitations probably due to chemical etching.