TABLE 3

Binding affinities of catechol agonists for wild-type human D₁ and TM5 serine mutant receptors

Data represent means ± S.E.M. from at least four independent competitive binding experiments performed with [³H]SCH 23390. K_i values were calculated from IC₅₀ values of one-site sigmoidal curves (with Hill slopes <1) as described under Materials and Methods. Statistical significance was determined from pK_i values.

Ligand	K_i
Ligand	hD₁ WT	S198A	S199A	S202A
	nM
DA	1010 ± 230	4700 ± 1200^**	13,000 ± 3700^**	54,400 ± 1500^**
Cyclohexyl isochroman	13.1 ± 2.4	464 ± 140^**	402 ± 70^**	1200 ± 91^**
Cyclohexyl carbocylic	183 ± 13	2800 ± 690^**	3240 ± 690^**	7610 ± 620^**
Cyclohexyl chroman	2110 ± 140	5210 ± 1400^*	10,500 ± 2400^**	27,900 ± 2900^**
Apomorphine	274 ± 52	700 ± 150^*	669 ± 99^*	4780 ± 360^**
Dinapsoline	110 ± 16	689 ± 190^**	885 ± 180^**	3950 ± 420^**
Dihydrexidine	114 ± 11	1370 ± 170^**	2680 ± 470^**	3430 ± 260^**
Doxanthrine	238 ± 69	1150 ± 320^*	2660 ± 660^**	6160 ± 400^**
SKF 38393	290 ± 28	2140 ± 600^**	1440 ± 310^**	860 ± 110^*
SKF 81297	18.8 ± 3.6	213 ± 50^**	365 ± 29^**	68.5 ± 12^**
SKF 82958	9.16 ± 2.7	390 ± 190^**	173 ± 17^**	42.2 ± 9.7^*
SKF 83959	1.19 ± 0.3	66.6 ± 15^**	29.5 ± 11^**	5.23 ± 1.7^*

↵* Significantly different from wild-type (p < 0.05).
↵** Significantly different from wild-type (p < 0.01).