Different effect of GABA on temperature
regulation during rest and exercise in hot ambient temperature
Taiki Miyazawa
Department of environmental physiology for exercise, Graduate school
of medicine,
Background: Centric administration of GABA affects temperature
regulation in animals. We investigated the effects of the oral administration
of GABA on temperature regulation during rest and exercise in man. Methods:
Eight male subjects drunk a sports drink of 200 ml with GABA of 1 g (GABA
drink; GR) or without GABA (placebo; CR) and rested for 60 min in a hot environment
(Ta=35°C, RH =50%). Another 8 male subjects drunk the GABA drink (GEx) or placebo (CEx), rested for
30 min and conducted pedaling exercise for 30 min in the same condition. Esophageal
temperature (Tes), oxygen consumption rate
(VO2), and plasma catecholamine concentrations (Cats) were measured
throughout the tests, and sweat loss throughout test was evaluated. Results: There
were no changes in Tes and VO2
during CR, while those during GR were significantly lower than values before drinking and also
than CR. In CEx, Tes
and Cats were increased by exercise, while the magnitude of increase in GEx was significantly attenuated compared with CEx. Additionally, sweat loss in GR and GEx
was significantly lower than CR and CEx,
respectively. Conclusions: The oral administration of GABA decreased Tes, VO2, and sweat loss in rest,
while attenuated increases in Tes, Cats,
and sweat loss during exercise.
Key words: GABA, Temperature regulation,
Sweat loss