Abstract
Although it is known that GABA(B) receptors are negatively coupled to adenylyl cyclase, the detailed selectivity of functional interaction between GABA(B) receptors and Gi subfamily members is still ambiguous. (+/-)-Baclofen-stimulated high-affinity GTPase activity, which was competitively antagonized by 2-hydroxy-saclofen, was attenuated by pretreatment of the membranes with N-ethylmaleimide (NEM) in a concentration- and incubation period-dependent manner. The NEM-pretreated (50 microM, 15 min at 4 degrees C) membranes restored the (+/-)-baclofen-sensitive high-affinity GTPase activity when reconstituted with pertussis toxin-sensitive bovine brain G proteins. Among recombinant rat Galpha subunits, G(i alpha(-2)) appeared most effective as compared with other subunits (G(i alpha(-2)) > G(i alpha(-3) > G(i alpha(-1) = G(o alpha). The GABA(B) receptor-mediated high-affinity GTPase activity was also completely eliminated by 100 microM suramin and by 100 microM benzalkonium chloride. These results indicate that GABA(B) receptors in rat cerebral cortex couple to NEM-sensitive G proteins, in particular Gi2, which are sensitive to suramin and benzalkonium chloride.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenylate Cyclase Toxin
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Animals
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Baclofen / analogs & derivatives*
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Baclofen / pharmacology
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Benzalkonium Compounds / pharmacology*
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Cell Membrane / drug effects*
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Cell Membrane / metabolism
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Cell Membrane / ultrastructure
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Cerebral Cortex / drug effects
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Cerebral Cortex / metabolism
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Cerebral Cortex / ultrastructure
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Dose-Response Relationship, Drug
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Ethylmaleimide / pharmacology*
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GABA Antagonists / pharmacology
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GTP Phosphohydrolases / drug effects
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GTP Phosphohydrolases / metabolism
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GTP-Binding Proteins / drug effects*
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GTP-Binding Proteins / metabolism
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Male
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Neurons / drug effects
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Neurons / metabolism
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Neurons / ultrastructure
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Pertussis Toxin
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Rats
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Rats, Sprague-Dawley
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Receptors, GABA-B / drug effects*
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Receptors, GABA-B / metabolism
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Subcellular Fractions / drug effects*
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Subcellular Fractions / metabolism
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Subcellular Fractions / ultrastructure
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Suramin / pharmacology*
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Virulence Factors, Bordetella / metabolism
Substances
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Adenylate Cyclase Toxin
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Benzalkonium Compounds
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GABA Antagonists
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Receptors, GABA-B
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Virulence Factors, Bordetella
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Suramin
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Pertussis Toxin
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GTP Phosphohydrolases
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GTP-Binding Proteins
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Baclofen
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saclofen
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Ethylmaleimide