Modulation of GABA(A) receptors by benzodiazepines and barbiturates is autonomous of PKC activation.
Previous studies have suggested that activation of calcium-phospholipid-dependent protein kinase (PKC) enhances benzodiazepine (BZD)- and pentobarbital (PB)- mediated potentiation of alpha(1)beta(1)gamma(2) GABA(A) receptors (GABA(A)-Rs). To delineate the underlying mechanism(s), voltage-clamp recordings were performed on recombinant alpha(1)beta(1)gamma(2) GABA(A) receptors functionally expressed in Xenopus laevis oocytes. GABA(A)-Rs were tested for their sensitivity to diazepam and PB before and after incubation in phorbol 12-myristate 13-acetate (PMA). PMA (25 nM) significantly attenuated the GABA(A) current (p<0.05, n=12-19) up to 90%. PMA treatment, however, did not alter the sensitivity to diazepam or pentobarbital. Similar results were obtained with recombinant alpha(1)beta(2)gamma(2) GABA receptors. These data suggest that PKC activation does not alter the allosteric modulation of GABA(A)-Rs by benzodiazepines and barbiturates and is consistent with the observation from other studies in oocytes that PMA decreases the amplitude of the GABA-activated currents via receptor internalization rather than modification of receptor kinetics.
Ghansah
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Department of Neurobiology, University of Alabama at Birmingham, School of Medicine, 1719 Sixth Avenue South, CIRC 410, Birmingham, AL 35294-0021, USA.
Weiss
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D000494:Allosteric Regulation / Q000187:drug effects; D000818:Animals; D001463:Barbiturates / Q000494:pharmacology*; D001569:Benzodiazepines / Q000494:pharmacology*; D002478:Cells, Cultured; D003975:Diazepam / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D018757:GABA Modulators / Q000494:pharmacology; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010424:Pentobarbital / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D021122:Protein Subunits; D051381:Rats; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014982:Xenopus laevis
D001463:Barbiturates; D018757:GABA Modulators; D006993:Hypnotics and Sedatives; D021122:Protein Subunits; D011963:Receptors, GABA-A; D011994:Recombinant Proteins; D001569:Benzodiazepines; D011493:Protein Kinase C; D010424:Pentobarbital; D013755:Tetradecanoylphorbol Acetate; D003975:Diazepam