GABA ring, size 6.
GABA or gamma-aminobutyric acid is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays the principal role in reducing neuronal excitability throughout the nervous system. In humans, GABA is also directly responsible for the regulation of muscle tone. Drugs that increase the available amount of GABA typically have relaxing, anti-anxiety, and anti-convulsive effects