Abstract
Introduction: Gamma-aminobutyric acid (GABA) is a depressive neurotransmitter, distributed in central nervous system. It has been reported that oral administration of GABA induces antihypertensive effects and a depressing of mental stress at rest. But it is unknown about the effect and the mechanism of GABA oral administration during exercise. We investigated the effect of oral administration of GABA on thermoregulation in man at rest and during exercise and the mechanism underlying this effect. Methods: Eight healthy male subjects drunk a sports drink of 200ml with GABA of 1 g (trial-G) or without GABA (trial-C), rested for 20 min and conducted pedaling exercise of 65% VO2max for 30 min in hot environment (Ta=35°C, RH=40%). We measured esophageal temperature for core temperature, physiological responces. Results: At rest, core temperature (Tes) was slightly increased in trial-C while there was no change in Tes in trial-G. During exercise Tes increased 1.95 ± 0.04 °C in trial-C and 1.79 ± 0.03 °C in trial-G. Increase of blood pressure, heart rate, plasma adrenaline concentration and plasma noradrenaline concentration during exercise were depressed in trial-G compared with those in trial-C. Conclusion: These results suggest that oral administered GABA depressively affects on central thermoregulatory system in hypothalamus and causes the set point shift to the low temperature side. [J Physiol Sci. 2008;58 Suppl:S101]
