Table 1. Affinity of clozapine and its metabolites to NMS binding site.

Compound	hM1	hM2	hM3	hM4	hM5
Acetylcholine	14 ± 1.8 μM	1.8 ± 0.2 μM	9.5 ± 0.8 μM	12 ± 1.9 μM	15 ± 0.9 μM
Clozapine	13 ± 2	51 ± 4	25 ± 2	33 ± 4	26 ± 3
N-desmethylclozapine	55 ± 5	1,650 ± 101	223 ± 30	344 ± 25	105 ± 8
Clozapine-N-oxide	2.5 ± 0.3 μM	33 ± 3 μM	8 ± 0.7 μM	4 ± 0.3 μM	2.5 ± 0.2 μM

IC₅₀ values are the mean ± SEM of three experiments performed in quadruplicate. IC₅₀ are expressed in nM except otherwise indicated. [³H] NMS concentration was 200 pM.