Desensitization characteristics of rat recombinant GABA(A) receptors consisting of alpha1beta2gamma2S and alpha1beta2 subunits expressed in HEK293 cells.

Desensitization kinetics of rat recombinant typeA GABAergic receptors consisting of the subunits alpha1beta2gamma2S or alpha1beta2 was investigated on application of 10-0.001 mM GABA to whole cell patches using a piezo driven liquid filament switch for fast application and deapplication. At high GABA concentrations desensitization was triphasic showing increasing time constants and a decreasing extent of desensitization on lowering the GABA concentration. Below agonist concentrations of 1 mM for the trimeric receptor and 0.1 mM for the dimeric one desensitization was biphasic switching to monophasic kinetics at GABA concentrations < or = 0.01 mM for the alpha1beta2gamma2S-type and < or = 0.003 mM for the alpha1beta2-type, respectively. Comparison with former studies performed with GABAergic receptors consisting of different subunits revealed differences in the desensitization kinetics.