[Energy metabolism in the cerebrum and the brainstem-cerebellum of the rat brain under hypoxic conditions].
The relationship between neuronal activity, intracellular oxygenation and energy metabolism in the cerebrum and the brainstem-cerebellum of the rat brain in graded hypoxia was studied. Intracellular oxygenation was monitored by near-infrared measurement of the redox state of cytochrome oxidase (cyt.ox.). Neuronal activity was assessed by EEG (electroencephalography) and the evoked potentials (VEP; visual, BSR; brainstem, C-SEP; cortical-sensory, S-SEP; spinal-sensory evoked potentials). As hypoxia progressed, neuronal activities disappeared in the order of VEP, C-SEP, EEG, BSR, S-SEP. However, intracellular oxygenation at the disappearance of each neuronal activity was significantly lower in the brainstem-cerebellum than in the cerebrum. ATP (adenosine triphasphate), glucose, and lactate were measured in the cerebral cortex, subcortex, brainstem, and cerebellum 1-2 minutes after the disappearance of neuronal activities on EEG. Hypoxia caused decreases in ATP in each brain region. Marked increases in lactate were observed in each brain region, though the degree of increment was less in the cerebral cortex than the other brain regions. A decrease in glucose was observed only in the cerebral cortex. These results suggest that by the use of the energy generated via glycolysis, the brainstem functions even after oxygen supply has been significantly reduced, while the neuronal activity in the cerebrum is suppressed at the higher oxygenation level than that in the brainstem-cerebellum. It is, thus, supposed that these differential responses of brainstem and cortical neurons to oxygen deprivation are inherent, and critical for neuronal survival in severe hypoxia.
Mizukami
S
S
Department of Pediatrics, Hokkaido University School of Medicine, Sapporo, Japan.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D001933:Brain Stem / Q000378:metabolism*; D002531:Cerebellum / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D004569:Electroencephalography; D003576:Electron Transport Complex IV / Q000378:metabolism; D004734:Energy Metabolism; D005071:Evoked Potentials; D005947:Glucose / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D007773:Lactates / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000378:metabolism; D010101:Oxygen Consumption; D051381:Rats; D017208:Rats, Wistar
D007773:Lactates; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV; D005947:Glucose