Distribution of GABAA and GABAB receptors in mammalian brain: Potential targets for drug development

GABA is the major inhibitory neurotransmitter in mammalian brain. GABA receptors and the metabolism of GABA are significant targets for new centrally acting drugs to treat neurological and behavioral disorders. The simple neutral amino acid is likely to subserve a neurotransmitter role at 25–50% of all synapses in the central nervous system. GABA's actions are mediated by two different receptors, GABA_A and GABA_B receptors. GABA_A receptors are ligand-gated chloride channels that are sensitive to the convulsant alkaloid bicuculline and modulated by benzodiazepines and barbiturates. GABA_B receptors affect calcium and potassium conductance through GTP binding proteins and are insensitive to bicuculline and sensitive to the agonist baclofen. Both receptors are widely distributed in cerebral cortex, hippocampus, basal ganglia, thalamus, cerebellum, and brainstem.