Table 2.

Binding affinities of original lead compound 2 and new compounds 11-23 at the D₁-like, D₂-like, and D₃ receptors in binding assays using rat brain preparation.

ligand	R	Ki±SEM (nM)		Selectivity
		D3	D2-like	D1-like	D2-like/D3	D1-like/D3
2		0.40±0.087	725±45	1,610±167	1,827	4,025
11		0.74±0.038	224±9	1,970±179	301	2,662
12		0.62±0.068	72±11	49,700±2,807	117	80,161
13		0.58±0.062	101±12	28,700±2,640	175	49,482
14		1.6±0.19	244±46	15,113±780	157	9,751
15		0.46±0.06	17,000±4,092	53,600±8,380	36,956	116,521
16		1.9±0.087	264±46	56,600±2,730	138	29,789
17		0.89±0.17	367±27	50,000±4,890	412	56,180
18		0.43±0.06	6,950±1,095	28,200±5,308	16,272	65,581
19		1.0±0.094	158±25	43,500±711	160	44,500
20		0.70±0.055	2,660±461	42,800±3,279	3,779	61,143
21		0.76±0.036	9,790±1,500	64,200±1,760	12,836	84,474
22		0.96±0.10	14,600±1,280	19,200±2,550	15,208	20,000
23		0.53±0.07	15,800±5,910	15,000±2,920	29,800	28,300

D₃ receptor binding was determined using [³H]7-OH-DPAT and membranes prepared from ventral striatum.

D₂-like receptor binding (D₂, D₃, and D₄) was determined using [³H]spiperone and striatal membranes. D₂-like receptor binding (D₂, D₃, and D₄) was determined using [³H]spiperone and striatal membranes. For those compounds that produced a competition curve consistent with inhibition at 2-sites in this assay, which is consistent with the behavior of agonists in this assay, the K_i value for the high affinity component is reported. D₁-like receptor binding (D₁ and D₅) was determined using [³H]SCH23390 and striatal membranes.

Data are the mean ± SEM of 3–6 independent determinations.