γ-Aminobutyric acid

γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system. GABA is synthesized from glutamate by glutamate decarboxylase. GABA acts by binding to two types of GABA receptors of pre- and postsynaptic neurons, an ionotropic receptor, GABAA, and a metabotropic receptor, GABAB. The ionotropic GABAA has binding sites for benzodiazepines, barbiturates, and neurosteroids in addition to binding sites for GABA. In the pancreas, β-cells secrete GABA along with insulin. GABA inhibits glucagon secretion from α-cells. GABA also promotes the replication and survival of β-cells and the conversion of α-cells to β-cells. Therefore, GABA may improve therapies for diabetes. GABA also regulates immune responses. GABA exhibits both excitatory and inhibitory actions in insects.