[Damage of the cochlea and of the cochlear nucleus after the application of aminoglycosid antibiotics--a comparative light-, transmission- and scanning electronmicroscopic study in the guinea pig (author's transl)].

Ototoxic alterations were studied in the guinea pig organ of Corti and in the cochlear nucleus after high administrations of aminoglycosid antibiotics (Gentamicin/Tobramycin, 150 mg/kg body weight/day or Amikacin 300 mg/kg body weight for 10 days). After survival times up to 22 days the animals were examined. By means of morphology degeneration was found in the cochlear nucleus before we could state it in the organ of Corti. After longer survival times, when we observed heavy degeneration in the organ of Corti we found only a few myelin figures of axons in the cochlear nerve. Cochlear nucleus: As an early sign of degeneration alterations in the mitochondria were found. Compared with the organ of Corti the damage was less widespread in the second order neurons of the afferent auditory pathways, their dendrites or nerve endings. Quantitative calculations however, were not performed. In axosomatic synapses we could observe a way of degeneration which was not reported before in damage caused by aminoglycosid antibiotics. Free postsynaptic densities were observed to be invaginated into the neuron as a probable way of sequestration. As well we could observe reoccupation of the synaptic sites by a probable sliding of neighbouring nerve endings into the free intracellular space. (Similar observations were reported first by Gentschev and Sotelo [1973] after ablation of the cochlear nerve in rats.