The relationship between cortical electrical activity and regional cerebral glucose metabolic rate in rats exposed to 3 atmospheres absolute oxygen.

The regional cerebral metabolic rate for glucose (rCMRgl) was autoradiographically measured in conscious rats during 180-210 min of exposure to 3 atmospheres absolute oxygen (ATA O2), 3 ATA N2-O2 normoxia and air at 1 ATA. The exposure time and oxygen pressure in the present study were purposely matched to a parallel project in human subjects. The electrocorticogram (ECoG) was continuously recorded throughout the exposure. According to the ECoG responses, the oxygen-exposed rats fell into two categories: 'resistant' ones, those without changes in ECoG throughout the exposure; and 'sensitive' rats, those with changes in EcoG before or during the rCMRgl measurements. The observed ECoG changes were increased slow wave activity in the delta range, which was in some cases followed by paroxysmal electrical discharges. No changes in rCMRgl were observed in oxygen-exposed 'resistant' rats as compared to air breathing or N2-O2 normoxic rats at 3 ATA. However, in the 'sensitive' rats there were increases in rCMRgl in 8 of the 28 neuroanatomical structures examined as compared to the air breathing and 3 ATA normoxic controls. It is concluded that the increase in rCMRgl are related to the onset of the oxygen-induced preconvulsive changes in ECoG.