GABA

Definition and Mechanisms of Action

Gamma(γ)-aminobutyric acid (GABA) is considered to be the major inhibitory neurotransmitter in the central nervous system (CNS). It is the product of decarboxylation, via l-glutamic acid decarboxylase (GAD), of glutamate and is thus an amino acid-derived neurotransmitter. This neurotransmitter and its respective receptors, the ionotropic GABA_A receptor and the metabotropic GABA_Breceptor, are found throughout the CNS and are targets of drug action in an attempt to affect GABA, or its receptors, to cause anxiolytic, hypnotic, anesthetic, anticonvulsant, or muscle relaxant effects. Interestingly, GABA is derived from the same source as the brain’s most common excitatory neurotransmitter, glutamate, and often acts in opposition to glutamate to achieve a balance between excitation and inhibition at the synaptic level. The role of GABA is to bind to, and activate, a ligand-gated chloride ionophore channel complex to increase the entry of chloride ions...