The Journal of pharmacology and experimental therapeutics
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J. Pharmacol. Exp. Ther. · Nov 2004
Compounds exhibiting selective efficacy for different beta subunits of human recombinant gamma-aminobutyric acid A receptors.
Inhibitory GABA(A) receptor modulators are widely used therapeutic agents for a variety of central nervous system disorders. Ltk(-) cells stably expressing human recombinant GABA(A) subunits (alpha1beta1-3gamma2s) were seeded into 96-well plates, loaded with chlorocoumarin-2-dimyristoyl phosphatidylethanolamine and bis(1,3-diethyl-2-thiobarbiturate)trimethineoxonol, and rapid fluorescence resonance energy transfer technique (FRET) measurements were made of GABA-evoked depolarizations in low-Cl(-) buffer using a voltage/ion probe reader. The influence of different betasubunits on the ability of agents to modulate and directly activate the ion channel was examined. ⋯ Diflunisal was the most efficacious compound, eliciting greater potentiation than loreclezole (90 +/- 14% and 109 +/- 14% at beta3 and beta2, respectively, compared with 62 +/- 6% and 56 +/- 3%), whereas niflumic acid exhibited the lowest efficacy. An additional agent, olsalazine, weakly potentiated responses at all three receptors without any selectivity. This study identifies and characterizes a variety of allosteric modulators for which betasubunits are an important determinant of efficacy and potency.