gamma-Aminobutyric acid-d2 is the deuterium labeled gamma-Aminobutyric acid. gamma-Aminobutyric acid (4-Aminobutyric acid) is a major inhibitory neurotransmitter in the adult mammalian brain[1][2], binding to the ionotropic GABA receptors (GABAA receptors) and metabotropic receptors (GABAB receptors)[2].