GABA is the main inhibitory neurotransmitter in the adult human central nervous system.
GABA stands for gamma-aminobutyric acid. It is released by specialized neurons and usually reduces the likelihood that a receiving neuron will generate an action potential. This inhibitory signaling helps control the balance between excitation and inhibition that allows neural circuits to operate reliably.
GABA commonly acts through GABA-A receptors, which are ion channels, and GABA-B receptors, which are G-protein-coupled receptors. GABA-A receptor activity is enhanced by several important drugs, including benzodiazepines and barbiturates. The sedative effects of alcohol also involve multiple targets, including GABA-related signaling.
GABA’s role changes during early development. In immature neurons, differences in chloride concentration can make GABA responses depolarizing rather than strongly inhibitory. This is one reason the phrase “main inhibitory neurotransmitter” is most accurate for the mature central nervous system. Glutamate is the major excitatory counterpart, and healthy brain function depends on interaction between the two systems rather than either transmitter acting alone.