Table 3.

Main electrophysiological parameters of the different GABA_A receptor subtypes in standard ionic conditions (subunits expressed in mouse L929 cells)

GABAA receptor subtype	Single-channel conductance (pS)	GABA EC50 (µM)	Hill coefficient	Characteristic time of desensitization td (s)	Characteristic time of deactivation (ms)	Activation time (ms)
α1β1γ1		5.2 [165]
α1β1γ2	30 [125] (γ2L splice variant) 29.3 [145] (γ2S splice variant)	7.1 [146] 5.2 [168] (γ2L splice variant) 5.1 [169] (γ2L splice variant) 6.2 [125] (γ2L splice variant)	1.7 [146] 1.9 [168] (γ2L splice variant) 1.9 [169] (γ2L splice variant) 1.4 [125] (γ2L splice variant)		5 [125] (γ2L splice variant) 6.0 [145] (γ2S splice variant)
α1β1δ	22 [125]			No desensitization observed [125]	400 [125]
α1β2γ2	29 [145] (γ2S splice variant)	11 [171]
α1β3γ2	25.9 [114] 26.8 [130]	14 [171] 11.6 [130] (γ2L splice variant) 15.5 [111] (γ2L splice variant) 15.5 [182] (γ2L splice variant)	1.48 [111] (γ2L splice variant) 1.5 [182] (γ2L splice variant)	0.462 [114] ([GABA] = 1 mM, γ2L splice variant)	76.1 [114] (γ2L splice variant)	0.46 [114] (γ2L splice variant)
α1β3δ	23.8 [114] 26.7 [130]	2.8 [130] 4.4 [182]	1.4 [182]	1.26 [114] ([GABA] = 1 mM)	42.8 [114]	2.4 [114]
α1β3ε	24 [161] (rat α1 and β3, and human ε, in L929 cells)	0.8 [161] (rat α1 and β3, and human ε, in L929 cells)	0.9 [161] (rat α1 and β3, and human ε, in L929 cells)
α2β3γ2		25 [111] (γ2L splice variant)
α3β3γ2		35.8 [111] (γ2L splice variant)
α4β3γ2		10.7 [111] (γ2L splice variant) 2.57 [113]	1.3 [113]	2.5 [113] ([GABA] = 100 µM)
α4β3δ		0.5 [113]	1.3 [113]	4.8 [113] ([GABA] = 100 µM)
α5β1γ2		32.8 [157] (γ2L splice variant) 26 [124] (γ2L splice variant)	1.69 [157] (γ2L splice variant)
α5β3γ2	22 [133] (γ2L splice variant)	5.7 [157] (γ2L splice variant) 6 [124] (γ2L splice variant) 9.4 [111] (γ2L splice variant)	1.54 [157] (γ2L splice variant)		51.8 [133] (γ2L splice variant)	0.9 [133] (γ2L splice variant)
α5β3γ3	26.9 [191]	1.5 [191]	1.6 [191]
α5β3π	23.8 [191]	1.3 [191]	1.4 [191]
α6β2γ2		2 [171]
α6β2δ		0.2 [171]
α6β3γ2		2 [171] (γ2L splice variant) 2.25 [111] (γ2L splice variant)	1.04 [111] (γ2L splice variant)
α6β3δ		0.3 [171]

Roman: rat subunits; bold: human subunits; italics: bovine subunits. The Hill coefficient, GABA EC50, main conductance state and characteristic times of activation, deactivation and desensitization of the most abundant subtypes in vivo, i.e. ternary subtypes and ρ homopentamers, are presented. Information on other subtypes can be found in [13, 103, 112, 114, 116, 123, 125, 130, 146, 152–157, 176, 180, 182, 191, 192]