γ-アミノ酪酸（GABA）の投与が繰り返しストレス下のラットの肝臓および脳のGABA 代謝に及ぼす影響

抄録

Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmission compound found in the vertebrate brain. GABA has recently been attracting attention as a functional food with its anti-stress effect. However, the bioactive mechanisms of dietary GABA have not been fully clarified. We investigated in this study the biosynthesis and catabolism of GABA in the liver and brain of rats under repeated stress and GABA administration. After repeated restraint stress (16 hours a day for 7 days a week), a decrease in the liver weight and food intake were apparent. In addition, the glutamate decarboxylase (GAD) 65 gene expression was significantly increased in the liver, and the GABA concentrations in the liver and plasma were also significantly increased. In contrast, when GABA (100mg/100g of body weight) was orally administered to the rats, while the concentrations of GABA in the liver and plasma were significantly increased, the mRNA expression of GAD and GABA transaminase (GABA-T) remained unchanged.These results show that, under repetitive stress for 7 days, GABA biosynthesis in the liver was enhanced, and then the GABA concentrations in the liver and plasma increased. While dietary GABA resulted in an increase in GABA concentrations in the liver and plasma, it did not affect the gene expression of the enzymes responsible for GABA biosynthesis and catabolism. The GABA concentration in the brain was unaffected by GABA administration and stress application, and remained constant.