Experimental lipidosis of the inner ear. Morphological and functional results.

Chronic administration of chlorphentermine in young rats induces an accumulation of lysosomes containing phospholipids in the inner ear. The inner hair cells, the dark cells of the stria vascularis, the perikarya of the spiral ganglion and some supporting cells are those most affected, whereas the outer hair cells always remain free. Most of the nerve fibres coursing radially to the inner hair cells as well as some tunnel crossing and outer spiral fibres are swollen, filled with osmiophilic material and vacuoles and sometimes degenerated. After discontinuing the treatment the changes remain, though to a lesser degree. The inclusions lead to changes in the cochlear compound action potential. The threshold, the latency of the first component and the time difference of the individual components are clearly changed at higher sound levels. After stopping chlorphentermine feeding the hearing ability improves but it does not become normal. Since the inclusions are found mainly in the inner hair cells and nerve fibres, we assume that the lipid turnover in these structures is especially high.