Table 2. Antagonist potencies and selectivities of nuciferine (3a) and roemerine (3b) enantiomers for α₁ receptor subtypes calculated from pIC₅₀ curves.

	pKb a			K b (nM)			Subtype selectivity b
Compound	α1A	α1B	α1D	α1A	α1B	α1B	α1A/α1B	α1A/α1D	α1B/α1D
(R)-Nuciferine	7.42 ± 0.07	7.22 ± 0.01	6.78 ± 0.01	37.8	60.6	165	2	4	3
(S)-Nuciferine	7.17 ± 0.08	6.50 ± 0.01	6.94 ± 0.01	67.1	316	116	5	2	0.4
(R)-Roemerine	6.47 ± 0.08	6.57 ± 0.05	7.34 ± 0.15	338	266	46.0	0.8	0.1	0.2
(S)-Roemerine	7.07 ± 0.01	6.81 ± 0.03	7.04 ± 0.07	86.0	154	92.2	2	1	0.6
Prazosin c	9.69 ± 0.07	11.41 ± 0.09	10.60 ± 0.02	0.20	0.004	0.025	0.02	0.1	6

^aValues are expressed as mean ± SEM from at least 2 separate experiments.

^bSelectivities for receptor X/receptor Y were calculated as the ratio of K_{b receptor Y}/K_{b receptor X}.

^cPositive control.