[Evolutionary physiological analysis of body reactions to oxygen exposure under increase pressure]

In experiments on adult animals (rabbit, cat, dog), it has been found that changes during the initial stages of the effect of high oxygen pressure include: stabilization of the main rhythm of the EEG, inhibition of spindle-like activity and onset (or the increase) of interhemispheral asymmetry of the electrocorticogram, the increase of the amplitude of positive wave of primary response and slow negative wave of the evoked potential of the brain cortex, as well as the increase in the threshold level of inhibition of respiration in response to electrical stimulation of the cranial end of the vagal nerve and the increase in the stability of respiration and cardiac activity. These changes are similar to those which take place in the course of progressive evolution of functions of the central nervous system, respiratory and cardio-vascular systems in onto- and phylogenesis. On the basis of this parallelism, it is concluded that the initial (pre-toxic) effect of hyperoxia results in the increase of the activity of evolutionary younger functional systems of the brain. During the continuous effect of hyperoxia, oxygen intoxication of the organism takes place, which include particularly dissolution phenomena in the activity of the brain. These phenomena are most evident during the development of pre-seizure and seizure periods.