Excitability of the cortex in normal and adrenalectomized rats during repeated exposures to high oxygen pressure.

The excitability of the cortex in adrenalectomized and normal adult male rats to High Oxygen Pressure (HOP) was studied 2, 3, 4, 6, 8, 12 and 22 d after bilateral adrenalectomy and implantation of cerebral electrodes. Continuous electroencephalographic (EEG) recordings were obtained until the appearance of the first paroxysmal electrical discharges, which was considered to be the first indicator of the toxic effects of hyperbaric oxygen. A statistically significant change in excitability of the cortex to oxygen toxicity from 2 to 22 d following adrenalectomy was shown. Comparison of the sensitivity of the normal and adrenalectomized rats to HOP 2 d after the operation showed significant resistance of adrenalectomized rats at this time. This resistance disappeared gradually, when compared with normal rats, and cortical susceptibility increased significantly 22 d after adrenalectomy. The possible disturbances responsible for the changes in excitability of the cortex to HOP in adrenalectomized rats are discussed.