Effect of oral administration of GABA on temperature regulation in humans during rest and exercise at high ambient temperature.
BACKGROUND
Centric administration of gamma-aminobutyric acid (GABA) has been implicated to affect temperature regulation in animals during rest or under anesthesia. However, there are few reports concerning the effects of the oral administration of GABA on temperature regulation in humans during rest and exercise. In order to clarify the effects and underlying mechanisms, we measured several parameters related to temperature regulation of humans during rest and exercise at high ambient temperature (35 degrees C).


METHODS
On two occasions, eight endurance-trained men rested for 20 min and cycled at 65% VO2peak for 30 min. In control trial (trial-C), subjects drank the sample which was a sports drink of 200 mL (placebo) before the rest period. In another trial (trial-G), subjects drank the sample which was a sports drink containing 1000 mg of GABA (GABA drink) before the rest period.


RESULTS
In trial-G, the plasma GABA concentrations were maintained higher than those in trial-C during the experiment. An increase of esophageal temperature during rest and exercise was inhibited in trial-G. Sweat rate, and plasma catecholamine concentrations during exercise were inhibited in trial-G.


CONCLUSIONS
Esophageal temperature inhibition is suggested to be induced by the suppression of cold-sensitive neurons during rest, and the inhibition of plasma catecholamine concentrations caused by the GABA-induced attenuation of the sympathetic nervous system during exercise.
Miyazawa
Taiki
T
Department of Environmental Physiology for Exercise, Osaka City University, Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan. m2025873@med.osaka-cu.ac.jp
Kawabata
Takashi
T
Suzuki
Takashi
T
Imai
Daiki
D
Hamamoto
Takeshi
T
Yoshikawa
Takahiro
T
Miyagawa
Toshiaki
T
D000284:Administration, Oral; D000328:Adult; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D001833:Body Temperature Regulation / Q000187:drug effects* / Q000502:physiology; D004837:Epinephrine / Q000097:blood; D015444:Exercise / Q000502:physiology*; D018682:GABA Agents / Q000008:administration & dosage / Q000494:pharmacology*; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D012146:Rest / Q000502:physiology*; D013696:Temperature; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage / Q000494:pharmacology*
D018682:GABA Agents; D005680:gamma-Aminobutyric Acid; D009638:Norepinephrine; D004837:Epinephrine