Desensitization of GABA_ARs containing δ-γ2L chimeras. Desensitization and deactivation kinetics of GABA_ARs containing δ, γ2L, or δ-γ2L chimera subunits coexpressed with α1 and β3 subunits. Theleft column shows schematics of chimeras generated between the δ subunit (gray) and the γ2L subunit (white). N terminus is to the left (N-term), and boxes (1–4) indicate the four putative transmembrane domains. Representative normalized responses to a 400 msec pulse of 1 mm GABA are shown for each isoform in the center column. Desensitization was quantified as the relative contribution of a fast phase, %τ_fast (hatched bars, see Materials and Methods). Deactivation was fit with single or double exponential functions, and for comparison the weighted sum, τ_deact, is shown (solid bars). Note the different scales used for %τ_fast and τ_deact in the right column. The number of patches for each isoform is indicated in parentheses next to the sample currents. To facilitate comparison, shaded vertical bars indicate the mean (center of bar) and SEM range (thickness of bar) for wild-type αβδ and αβγ values of %τ_fast and τ_deact. Theasterisk indicates significant difference from both αβδ (p < 0.01) and αβγ (p < 0.05) receptors. Horizontal calibration: 400 msec; vertical calibration: 6 pA for δ, 2 pA for M2e, 68 pA for M1e, and 340 pA for γ2L.