THE EFFECT OF HYPOXIA ON BRAIN y-AMINOBUTRIC ACID LEVELS.
DEFENCE RESEARCH ESTABLISHMENT TORONTO DOWNSVIEW (ONTARIO)
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Animals were exposed to hypoxic environments either by supplying them with breathing mixtures low in oxygen or by exposing them in a decompression chamber to simulated altitude. Both methods of producing hypoxia brought about significant increases in brain gamma-aminobutric acid levels. Elevated gamma-aminobutyric acid levels occurred in all species tested moust, hamster, rat, guinea pig, and rabbit and reached maximal concentration 60 min after the initiation of breathing the hypoxic mixtures. Extension of the exposure beyond 60 min brought about a gradual decline in gamma-aminobutyric acid level from the maximal value reached. A linear relation was found between the oxygen content of the gas mixture and the elevation of gamma-aminobutyric acid level. For guinea pigs, at least, the critical oxygen content required to prevent elevation of gamma-aminobutyric acid level was 8.1 per cent. Author