Hyperthermia and brain neurotransmitter amino acid levels in infant rats.

1. The acute hyperthermia induced by exposure to elevated ambient temperatures (40 degrees C) during 90 min produced dramatic changes in certain brain transmitter amino acid levels in infant rats. 2. All inhibitor transmitter amino acids except taurine, rose significantly in 7 and 14 day-old rats. The effect of acute hyperthermia in excitatory transmitter amino acids was opposite, glutamic acid increased and aspartic acid decreased. 3. Taurine, that does not change during acute hyperthermia is the amino acid whose concentration suffers the greatest change with age. 4. The greater rise of body temperature in 21 day-old rats, was associated to slight changes in brain transmitter amino acid levels. These findings suggested that lower rise on body temperature found in 7 and 14 day-old rats may be related to the higher increase of inhibitor transmitter amino acids.