N,N-bis-pyrrolidonomethyl-diaza - 18-crown-6 and piracetam, which are structural analogues of gamma-aminobutyric acid (GABA) and exhibit nootropic properties, affected the GABA metabolism, the content of total protein, DNA and RNA in rat brain after long-term administration at pharmacologically active doses of 100 mg/kg and 400 mg/kg, respectively. As compared with control values, content of GABA in rat brain was increased by 40% after administration of N,N-bis-pyrrolodonomethyl-diaza-18-crown-6 and by 28%--after treatment with piracetam. At the same time, activity of GABA transaminase was decreased by 49.4% and 39.8%, respectively, while the decarboxylase activity was unaltered.