Gamma-aminobutyric acid (GABA) is a major neurotransmitter that is abundantly and widely distributed throughout the central nervous system (CNS). Within the brain, GABA is formed in neuronal cells by the a-decarboxylation of glutamic acid and further metabolized by GABA-a-keto-glutarate transaminase and then returned to the tricarboxylic acid cycle (TCA) cycle.