PHARMACOLOGY OF RECOMBINANT GAMMA-AMINOBUTYRIC ACIDA RECEPTORS RENDERED DIAZEPAM-INSENSITIVE BY POINT-MUTATED ALPHA-SUBUNITS

Amino acids in the alpha- and gamma-subunits contribute to the benzodi azepine binding site of GABA(A)-receptors. We show that the mutation o f a conserved histidine residue in the N-terminal extracellular segmen t (alpha 1(H101R), alpha 2(H101R), alpha 3(H126R) and alpha 5(H105R)) results not only in diazepam-insensitivity of the respective alpha x b eta 2,3 gamma 2-receptors but also in an increased potentiation of the GABA-induced currents by the partial agonist bretazenil, Furthermore, Ro 15-4513, an inverse agonist at wildtype receptors, acts as an agon ist at all mutant receptors, This conserved molecular switch can be ex ploited to identify the pharmacological significance of specific GABA( A)-receptor subtypes in vivo. (C) 1998 Federation of European Biochemi cal Societies.