Oral administration of γ-aminobutyric acid affects heat production in a hot environment in resting humans.
BACKGROUND
Central administration of γ-amino butyric acid (GABA) induces lower body temperature in animals in hot ambient air. However, it is still unknown whether oral GABA administration affects temperature regulation at rest in a hot environment in humans. Therefore, in the present study, we specifically hypothesized that systemic administration of GABA in humans would induce hypothermia in a hot environment and that this response would be observed in association with decreased heat production.


METHODS
Eight male participants drank a 200-ml sports drink with 1 g of GABA (trial G) or without GABA (trial C), then rested for 30 minutes in a sitting position in a hot environment (ambient air temperature 33°C, relative humidity 50%).


RESULTS
We found that changes in esophageal temperature from before drinking the sports drink were lower in trial G than in trial C (-0.046 ± 0.079°C vs 0.001 ± 0.063°C; P < 0.05), with lower heat production calculated by oxygen consumption (41 ± 5 W/m2 vs 47 ± 8 W/m2; P < 0.05).


CONCLUSIONS
In this study, we have demonstrated that a single oral administration of GABA induced a larger decrease in body core temperature compared to a control condition during rest in a hot environment and that this response was concomitant with a decrease in total heat production.
Department of Environmental Physiology for Exercise, Graduate School of Medicine, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. miyazawa29@toyo.jp
Taiki
T
Miyazawa
Takashi
T
Kawabata
Kazunobu
K
Okazaki
Takashi
T
Suzuki
Daiki
D
Imai
Takeshi
T
Hamamoto
Shinya
S
Matsumura
Toshiaki
T
Miyagawa
D000284:Administration, Oral; D000328:Adult; D000704:Analysis of Variance; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects; D004311:Double-Blind Method; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D010919:Placebos; D022722:Thermogenesis / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage*
D010919:Placebos; D005680:gamma-Aminobutyric Acid