Abstract
BackgroundCentral 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.MethodsEight 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%).ResultsWe 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).ConclusionsIn 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.
Highlights
Central administration of g-amino butyric acid (GABA) induces lower body temperature in animals in hot ambient air
On the basis of a previous study conducted in our laboratory, we have reported that oral GABA administration might induce lower core temperature during rest under a hot environment [12]
We 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
Summary
Eight male participants drank a 200-ml sports drink with 1 g of GABA (trial G) or without GABA (trial C), rested for 30 minutes in a sitting position in a hot environment (ambient air temperature 33°C, relative humidity 50%). Participants Eight healthy nonsmoking men who usually exercised 3 to 5 days per week were included in this study. Their physical characteristics were age 23.5 ± 3.6 years, height 172.6 ± 3.5 cm, weight 66.9 ± 7.4 kg, body mass index 22.5 ± 2.7 kg/m2 (all means ± SD). The dose was the maximal consumption of GABA for a single ingestion (Japan Standard Commodity Classification 872199). Both the placebo and the GABA drink were stored at room temperature controlled at 23°C to 25°C. The sports drink (200 ml) provided 30 kcal of energy, 7.4 g of carbohydrate, 0 g of protein and 0 g of fat
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