[On the effect of hyperbaric oxygen (OHP) at the guinea pig's cochlea insulted by hypoxia (author's transl)]

Specific activities of antioxidative enzymes in the cochlea of guinea pigs at different stages of development

Significant activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were found in the cochleas of guinea pigs of different ages. The specific activities of SOD and GSH-Px (expressed as units/mg protein) increased significantly from fetal animals to animals 2 days old and then to 6-month-old animals.

The effects of hyperbaric oxygen on experimental noise damage to the ears

The effect of hyperbaric oxygen on cochlear microphonics, action potential of the auditory nerve, and brain stem response damaged by short exposure to noise is varied. Of 26 guinea pigs 14 showed a positive influence as measured by amplitudes. In 12 animals oxygen had little or no effect. The reason for this could lie in the individual reaction to the anesthetic of the section of the auditory nerve tested. The reaction of postmortem cochlear microphonics after hyperbaric oxygen treatment indicates oxygen diffusion through the round window.

[The influences of hyperbaric oxygen (OHP) on the normal inner ear of guinea pigs. Simultaneous registrations of cochlea microphonics (CM) and nerve potentials (AP) (author's transl)]

Guinea pigs were treated with 3 bar oxygen pressure in a hyperbaric chamber and CMs and APs were simultaneously registrated. The results depended on the kind of the usual anesthesy. If nembutal i.p. was used, the CMs and APs had been increased significant shortly after oxygen pressure reached 3 bar (CMs increased more than APs). If urethane i.p. was used, the CMs and APs increases not so significantly. These results are traced back to the different effect of the both anesthetic drugs on the blood flow in the brain. Oxygen toxicity in the inner ear was observed after OHP of 3 bar more than 30 min but only by APs. The CMs didn't show any signs of oxygen toxicity under the same conditions during 60 min and more.