Table 1. Wild-type and Mutant GABA_A receptor functional characteristics in Xenopus oocytes.

Receptor	GABA EC50 (µM)	Max. GABA Efficacy a	ETO EC50 (µM)	Max. ETO Efficacy a	Spontaneous Activity b	EC50 Ratio (Ctl/3.2 ETO) c
α1β2γ2L	34±7	0.85±0.04	30±9.2	0.35±0.06	<0.002	17±3.5
	(n = 4)	(n = 4)	(n = 4)	(n = 6)	(n = 4)	(n = 4)
α1β2N265Cγ2L	31±5	0.91±0.05	35+5.7	0.02±0.006 **	<0.002 **	1.0±0.16 **
	(n = 4)	(n = 4)	(n = 3)	(n = 3)	(n = 5)	(n = 4)
β3-α1M236C/β3-α1M236C-γ2L	58±4.6*	0.63±0.08	40+3.9	0.60±0.10	<0.002	18±2.3
	(n = 4)	(n = 4)	(n = 3)	(n = 3)	(n = 3)	(n = 3)
β3N265M-α1M236C/β3N265M-α1M236C-γ2L	110±15**	0.60±0.12	n.a.	<0.002 **	<0.002	1.0±0.16 **
	(n = 3)	(n = 3)	(n = 3)	(n = 3)	(n = 3)	(n = 3)

^aEfficacy is the estimated fraction of activatable receptors that open in the presence of an agonist (either GABA or etomidate). The detection limit for etomidate agonist efficacy is about 0.2% of maximal GABA response.

^bSpontaneous activity is the estimated fraction of active receptors in the absence of either GABA or etomidate. The detection limit for spontaneous activity is about 0.2% of maximal GABA response.

^cEC₅₀ ratio is the ratio of control GABA EC₅₀ to GABA EC₅₀ measured in the presence of 3.2 µM etomidate. Large ratios indicate sensitivity to etomidate modulation.

*Differs from wild-type value at p<0.05. **Differs from wild-type value at p<0.01.