Table 1

Inhibition of [¹²⁵I]-labeled CGP64213 binding to chimeric and truncated GABA_B receptors by agonists and antagonists

	IC₅₀
	Agonist		Antagonist
	GABA	APPA	l-Baclofen	CGP47656^1-a	CGP64213	CGP54626	SCH50911
	μM
WT R1a	22.9 ± 2.4	2.3 ± 0.5	25.1 ± 7.8	10.8 ± 2.2	0.0023 ± 0.0001	0.0015 ± 0.0001	0.38 ± 0.03
WT R1b	31.1 ± 4.0	2.8 ± 0.2	35.1 ± 4.2	15.0 ± 2.4	0.0031 ± 0.0001	0.002 ± 0.0001	0.43 ± 0.04
aN1C	1.7 ± 0.33	0.3 ± 0.02	2.4 ± 0.4	1.2 ± 0.3	0.0018 ± 0.0001	0.0019 ± 0.0003	0.49 ± 0.05
aN7C	2.1 ± 0.1	0.25 ± 0.01	2.9 ± 0.3	1.4 ± 0.09	0.0021 ± 0.0002	0.002 ± 0.0012	0.41 ± 0.03
bN7C	1.9 ± 0.12	0.24 ± 0.023	3.1 ± 0.18	1.6 ± 0.4	0.002 ± 0.0001	0.001 ± 0.0002	0.6 ± 0.05
aN1	3.0 ± 0.11	0.29 ± 0.023	3.9 ± 0.45	1.3 ± 0.7	0.0017 ± 0.00006	0.003 ± 0.0009	0.42 ± 0.04
bN1	3.9 ± 0.45	0.21 ± 0.021	4.7 ± 0.58	1.4 ± 0.13	0.0023 ± 0.0003	0.0009 ± 0.0003	0.35 ± 0.03
sNa	6.8 ± 0.98	0.36 ± 0.12	13.3 ± 2.5	0.81 ± 0.29	0.0016 ± 0.0002	0.0021 ± 0.0004	0.27 ± 0.05
sNb	8.5 ± 0.99	0.67 ± 0.09	18.3 ± 1.2	2.3 ± 0.22	0.0011 ± 0.0001	0.0053 ± 0.002	0.35 ± 0.04

Membranes from COS cells transiently transfected with mutant cDNAs were used for radioligand binding. IC₅₀ values were obtained as described (Kaupmann et al., 1997) and are given as means ± S.E. of at least three experiments. Values for WT receptors were included for comparison (Kaupmann et al., 1997)

APPA, 3-aminopropylphosphinic acid.
↵1-a CGP47656 is a partial agonist (Kaupmann et al., 1997).