Gamma aminobutyric acid (GABA) is a neurotransmitter that is involved in regulating mood and sleep. GABA is one of the brain's main inhibitory neurotransmitters, meaning it acts as a regulator of neuronal activity, reducing their activity. Gamma-amino butyric acid can have an inhibitory effect on all types of nervous processes occurring in the spinal cord, in the cerebral cortex, in the brain stem and in other parts of the brain.