CHANGES IN BRAIN POTENTIALS DURING CONVULSIONS INDUCED BY OXYGEN UNDER PRESSURE

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Abstract
The effects of O2 poisoning on adult cats confined in a pressure tank were studied by means of the electroencephalograph (EEG). The O2 pressure was raised to 105 lb./sq. in. and maintained at that level throughout the expt. A normal EEG pattern persisted during the admn. of O2 at atmospheric pressure. Infrequent slow waves appeared shortly after pressure was applied. Volleys of slow waves appeared before the convulsion. The seizure was characterized by an ever increasing amplitude of 15-18/sec. activity. Following the motor discharge the EEG passed abruptly into an exhaustion phase during which there was complete absence of electric potential. Within a variable interval of time, slow waves of low amplitude reappeared and became more prominent until the next seizure occurred. Each preconvulsive phase was marked by more pronounced slow wave activity and by a diminution in the high frequency component. After each seizure the recovery time preceding the next one was prolonged. The EEG characteristics of the motor discharge phase remained quite constant. This EEG pattern was similar to that observed when other trigger agents were used to excite the motor discharge. From the known factors operating during the convulsion developed in O2 poisoning, it is postulated that the primary excitant in this condition is located intracellularly and that it probably is of an enzymatic nature. This confirms the postulate made in similar expts. on humans in which the climactic motor discharge was not attained.