Allosteric modulation of [3H]flunitrazepam binding to recombinant GABAA receptors.

Abstract The allosteric modulation of [ 3 H]flunitrazepam binding by γ-aminobutyric acid (GABA), pentobarbital, (+)-etomidate, etazolate, alphaxalone, propofol and chlormethiazole was investigated in cerebellar membranes from human embryonic kidney (HEK) 293 cells transfected with α 1 β 3 γ 2 or α 1 γ 2 subunits. Results obtained indicate that [ 3 H]flunitrazepam binding to recombinant GABA A receptors consisting of α 1 β 3 γ 2 subunits could be modulated by these compounds in a way and with a potency similar to that observed in cerebellar membranes. In addition, it was demonstrated that not only receptors consisting of α 1 β 3 γ 2 , but also those consisting of α 1 γ 2 subunits exhibited [ 3 H]flunitrazepam binding which could be stimulated by GABA. In contrast to α 1 β 3 γ 2 receptors, however, [ 3 H]flunitrazepam binding to recombinant α 1 γ 2 receptors was inhibited by pentobarbital, (+)-etomidate, etazolate, alphaxalone, propofol and chlormethiazole. This seems to indicate that binding sites for these compounds are present on α 1 γ 2 receptors, but that their allosteric interaction with [ 3 H]flunitrazepam binding sites is different from that of α 1 β 3 γ 2 receptors.