Effect of Escherichia coli endotoxin on cochlear potentials following its application to the chinchilla middle ear

The compound action potential (CAP) of the eighth nerve and the endocochlear potential (EP) were examined in the chinchilla as an animal model when Escherichia coli endotoxin (100 micrograms) was applied to the middle ear cavity. A significant elevation of the CAP threshold at 2, 3, and 4 kHz was observed 48 h after the instillation of endotoxin, but this hearing loss was thought to be caused by a conductive component. No significant change in the CAP threshold was recognized 30 days after instillation. The EP in either period showed no significant difference. These findings indicate that the application of endotoxin at the concentration used in the present study does not cause a cochlear disturbance.