[Molecular pharmacology of GABAA and GABAB receptors]

The receptor for gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter in the mammalian brain, has been classified into GABAA and GABAB subtypes. The GABAA receptor forms a Cl- channel and is consisted of several subunits. These subunits in the brain are known to be multiple and heterogeneous in their molecular structure. Therefore, it is suggested that these multiple GABAA receptors generate various inhibitory functions in the brain. In contrast, the GABAB receptor is known to be one of the metabotropic type of receptors which generate slow inhibitory postsynaptic potentials and functionally couple with Gi/Go types of GTP-binding proteins. The GABAB receptor in the brain has been purified to homogeneity using immunoaffinity purification procedures and found to be an 80-kDa protein. The possible existence of multiplicity in the cerebral GABAB receptor has also been suggested.