Table II.

Functional Properties of the ρ1 GABA_C Receptor Mutants at Positions R158 and D204

	Peak currents (nA)		EC50 (μM)		Hill coefficient, n		τ (s)
Receptor	GABA	Muscimol	GABA	Muscimol	GABA	Muscimol	GABA	Muscimol
WT ρ1	237–169	298–161	0.89 ± 0.01	1.05 ± 0.02	2.04 ± 0.06	1.53 ± 0.05	37.80 ± 10.06	5.97 ± 2.24
R158D	No response	No response	N/A	N/A	N/A	N/A	N/A	N/A
R158A	333–157	348–61	208.9 ± 19.66	110.2 ± 6.65	1.20 ± 0.10	1.41 ± 0.12	1.04 ± 0.36	1.17 ± 0.44
D204R	484–201	266–127	2.75 ± 0.13	5.3 ± 0.19	1.87 ± 0.08	1.36 ± 0.05	7.25 ± 1.83	1.81 ± 0.29
D204A	1003–530	51–28	12.4 ± 0.28	8.5 ± 0.52	1.53 ± 0.08	1.29 ± 0.09	1.89 ± 0.22	2.34 ± 0.54
R158D– D204R	No response	No response	N/A	N/A	N/A	N/A	N/A	N/A

The above data are the averages obtained from five or more different oocytes from two or more different batches. Dose-response data (mean ± SD for four to eight determinations in two to three experiments) for the wild-type (WT) human ρ1 GABA_C receptor as well as the mutant receptors are obtained by fitting of the Hill equation. Peak amplitudes of responses to GABA and muscimol for each mutant receptor are normalized to the saturating response obtained at the highest concentration of the respective agonist. τ values obtained by fitting a simple exponential to the recovery phase of the membrane current responses to the agonist concentrations in the range EC₃₀–E₇₀.