Allosteric modulation of [3H]flunitrazepam binding to recombinant GABAA receptors.
The allosteric modulation of [3H]flunitrazepam binding by gamma-aminobutyric acid (GABA), pentobarbital, (+)-etomidate, etazolate, alphaxalone, propofol and chlormethiazole was investigated in cerebellar membranes and membranes from human embryonic kidney (HEK) 193 cells transfected with alpha 1 beta 3 gamma 2 or alpha 1 gamma 2 subunits. Results obtained indicate that [3H]flunitrazepam binding to recombinant GABAA receptors consisting of alpha 1 beta 3 gamma 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 alpha 1 beta 3 gamma 3, but also those consisting of alpha 1 gamma 2 subunits exhibited [3H]flunitrazepam binding which could be stimulated by GABA. In contrast to alpha 1 beta 3 gamma 2 receptors, however, [3H]flunitrazepam binding to recombinant alpha 1 gamma 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 alpha 1 gamma 2 receptors, but that their allosteric interaction with [3H]flunitrazepam binding sites is different from that of alpha 1 beta 3 gamma 2 receptors.
Slany
A
A
Department of Biochemical Psychiatry, University Clinic for Psychiatry, Vienna, Austria.
Zezula
J
J
Fuchs
K
K
Sieghart
W
W
D000494:Allosteric Regulation; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005045:Etomidate / Q000494:pharmacology; D005445:Flunitrazepam / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D010424:Pentobarbital / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D011963:Receptors, GABA-A / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D005445:Flunitrazepam; D010424:Pentobarbital; D005045:Etomidate