Effects of ethanol on recombinant rat GABAA receptors: [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding study.
To determine the roles of the alternatively spliced short and long forms of the gamma 2 subunit in the effect of ethanol on the GABAA receptor function, picrotoxin-sensitive [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding was studied in recombinant rat alpha 1 beta 2 gamma 2 and alpha 6 beta 2 gamma 2 receptors expressed in human embryonic kidney 293 cells. Ethanol (10-500 mM) in the absence of added GABA had only minor effects on [35S]TBPS binding irrespective of the gamma 2 splice variant, its effects being greater in alpha 6 beta 2 gamma 2 than in alpha 1 beta 2 gamma 2 receptors. Ethanol (100 mM) decreased the binding in all four subunit combinations at various concentrations of GABA, again an effect independent of the gamma 2 variant. The two gamma 2 variants had different effects on GABA modulation of the binding, with the long gamma 2 variant decreasing the efficiency of GABA inhibition in alpha 6 beta 2 gamma 2 receptors and enhancing the biphasic GABA stimulation and inhibition in alpha 1 beta 2 gamma 2 receptors. The findings confirm the importance of the alpha subunits in the allosteric interactions between the convulsant binding site and other effector sites, which can be modified only to a minor extent by the type of the gamma 2 splice variant.
Korpi
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ER
Biomedical Research Center, Alko Ltd., Helsinki, Finland.
Herb
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Lüddens
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D000818:Animals; D001665:Binding Sites; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism* / Q000633:toxicity; D003292:Convulsants / Q000378:metabolism* / Q000633:toxicity; D000431:Ethanol / Q000633:toxicity*; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D051381:Rats; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013462:Sulfur Radioisotopes
D019086:Bridged Bicyclo Compounds, Heterocyclic; D003292:Convulsants; D011963:Receptors, GABA-A; D011994:Recombinant Proteins; D013462:Sulfur Radioisotopes; D000431:Ethanol; C037476:tert-butylbicyclophosphorothionate