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Benzodiazepine Treatment Causes Uncoupling of Recombinant GABA A Receptors Expressed in Stably Transfected Cells
Author(s) -
Klein Ronald L.,
Whiting Paul J.,
Harris R. Adron
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.63062349.x
Subject(s) - gabaa receptor , allosteric regulation , receptor , flunitrazepam , clonazepam , benzodiazepine , gabaa rho receptor , pharmacology , transfection , biology , chemistry , microbiology and biotechnology , biophysics , biochemistry , endocrinology , gene
GABA A and benzodiazepine receptors are allosterically coupled, and occupation of either receptor site increases the affinity of the other. Chronic exposure of primary neuronal cultures to benzodiazepine agonists reduces these allosteric interactions. Neurons express multiple GABA A receptor subunits, and it has been suggested that uncoupling is due to changes in the subunit composition of the receptor. To determine if uncoupling could be observed with expression of defined subunits, mouse Ltk − cells stably transfected with GABA A receptors (bovine α1, β1, and γ2L subunits) were treated with flunitrazepam (Flu) or clonazepam. The increase in [ 3 H]Flu binding affinity caused by GABA (GABA shift or coupling) was significantly reduced in cells treated chronically with the benzodiazepines, whereas the K D and B max of [ 3 H]Flu binding were unaffected. The uncoupling caused by clonazepam treatment occurred rapidly with a t 1/2 of ∼30 min. The EC 50 for clonazepam treatment was ∼0.3 µ M , and cotreatment with the benzodiazepine antagonist Ro 15‐1788 (5.6 µ M ) prevented the effect of clonazepam. The uncoupling observed in this system was not accompanied by receptor internalization, is unlikely to be due to changes in receptor subunit composition, and probably represents posttranslational changes. The rapid regulation of allosteric coupling by benzodiazepine treatment of the stably transfected cells should provide insights to the mechanisms of coupling between GABA A and benzodiazepine receptors as well as benzodiazepine tolerance.