Preliminary report on the effects of hyperoxia on cochlear potential in chinchilla.

Anesthestized chinchilla with round window electrodes were placed in a Plexiglas chamber. When they inhaled 100% oxygen at 1 atm, two types of neural effects were observed: 1. fast and reversible AP depression in response to brief exposure to 100% O2; and 2. a slowly developed chronic depression of AP and latency shift due to multiple hyperoxic exposures. The severity of the latter is a function of the dosage of the O2 inhaled, i.e., the concentration of oxygen and the length of time of exposure. For the type-1 effect, carbon dioxide deprivation is felt to be the immediate cause while the type-2 effect is mainly due to O2 toxicity developed at the intracellular level by high O2 concentration. The possible role of superoxide in the auditory O2 toxicity was discussed.