This study determined the influence of γ-aminobutyric acid (GABA) on brain protein synthesis via the mammalian target of rapamycin (mTOR) pathway. Experiments were carried out on three groups of 6-wk-old male rats with 0%, 0.5%, and 1% GABA. The percentage-phosphorylated S6K1 and growth hormone (GH) concentration was significantly increased by the GABA administration. The insulin level was not significantly changed, while the insulin-like growth factor 1 (IGF-1) level was significantly decreased by the GABA administration.