[Bioelectrical activity of the brain in rabbit fetuses in relation to the duration of umbilical cord occlusion]

Studies have been made on the EEG reactions in 20-, 25- and 28-day rabbit foetuses after complete occlusion of the umbilical cord. It was shown that in 20-day foetuses, EEG after the occlusion of the umbilical cord is presented mainly by low frequency waves. Significant decrease in the EEG amplitude took place to the 120th min, isoelectric stage was observed at the 150th min. In the frequency spectrum, the low frequency activity increased from 22.44 to 30.50%. As revealed by ECG control, the survival time after the occlusion of the umbilical cord is equal to 150 min. In 25-day foetuses, the decrease in the EEG amplitude was observed at the 150th min, isoelectric stage--to the 120th min. All the frequencies in the EEG spectrum were decreased. The survival time of foetuses was equal to 120 min. In 28-day foetuses, after the occlusion of the umbilical cord, a gradual decrease in the amplitude of EEG was observed from the 1st to the 60th min. Isoelectric stage occurred at the 105th min. Foetuses survived for 105 min. It is concluded that after the occlusion of the umbilical cord, re-arrangement in the EEG pattern takes place which includes two critical periods: the first one--immediately after the occlusion--is associated presumably with the reflex reaction of the organism of the foetus, whereas the second period includes the last minutes of survival, when a complete failure in the system of compensatory autoregulation is observed.