Expression of myeloperoxidase and cochlear dysfunction in the lipopolysaccharide-treated guinea pig

In this study, the effect of endotoxin on the guinea pig cochlea was examined by electrophysiology and immunohistochemistry. Bacterial lipopolysaccharide (LPS) was injected into the middle ear transtympanically. Electrocochleograms were measured immediately and 48 h after the injection with an electrode inserted into the facial canal. After the electrophysiological measurement, the animals were killed with an intracardiac perfusion of fixative and the temporal bones were removed and processed for immunohistochemistry with anti-myeloperoxidase (MPO) antibody. MPO could be detected after 48 h in the lateral wall and the organ of Corti. After injection of LPS, the threshold of the compound action potential worsened significantly at 48 h in the LPS group. These results suggest that MPO and reactive oxygen species are involved in cochlea dysfunction under inflammatory conditions.