TABLE 1

Characterization of radioligand affinity and expression for human D₁ WT, S198A, S199A, and S202A cell lines

Experiments were performed with [³H]SCH 23390 at D₁ receptors stably expressed in HEK cells. Values for K_d and B_max are expressed as means ± S.E.M. as calculated from at least seven independent experiments.

Cell Line	K_d	B_max
	nM	fmol/mg
HEK hD₁ WT^{^a}	1.2 ± 0.2	1840 ± 120
HEK hD₁ S198A^{^b}	51.6 ± 7.8^**	1610 ± 350
HEK hD₁ S199A^{^b}	27.5 ± 4.1^**	1990 ± 160
HEK hD₁ S202A^{^a}	1.1 ± 0.1	1890 ± 150

↵** Significantly different from wild-type (p < 0.01, one-way ANOVA with Dunnett's post-test).
↵a Generated by radioligand saturation binding.
↵b Generated by homologous competition binding.