GABA (Gamma-Aminobutyric acid) is a neurotransmitter in the central nervous system of mammals. GABA’s role changes from excitatory to inhibitory as the brain develops into adulthood. Normally, when a neuron receives an impulse, it will make the signal stronger, an inhibiting neurotransmitter prevents the cell from receiving the impulse, and the signal as a whole is weakened. In mammals, GABA regulates the extent to which neurons in the central nervous system will be stimulated. It plays a role in regulating neuronal excitability throughout the nervous system. In humans, GABA is also directly responsible for the regulation of muscle tone. Even though chemically it is an amino acid, GABA is rarely referred to as such in the scientific or medical communities. The term ‘amino acid,’ used without a qualifier, refers to the alpha amino acids, which GABA is not. GABA is also not incorporated into proteins.