Table 3.

Binding affinities of new compounds 24-35 at the D₁-like, D₂-like, and D₃ receptors in binding assays using rat brain preparation.

		Ki±SEM (nM)		Selectivity
ligand	R	D3	D2-like	D1-like	D2-like/D3	D1-like/D3
24		1.9±0.17	81±11	57,000±2,830	42	30,000
25		2.3±0.22	170±18	1,810±93	75	800
26		1.6±0.16	160±8.5	36,500±2,243	98	22,812
27		1.6±0.090	102±15	2,610±255	65	1,631
28		0.59±0.057	286±49	94,900±7,620	485	160,847
29		2.5±0.15	71±4.8	68,000±2,300	28	27,200
30		2.6±0.20	542±79	45,900±2,490	205	17,654
31		1.0±0.072	619±68	109,000±2,500	614	109,000
32		1.2±0.091	110±14	117,000±10,170	91	97,500
33		1.9±0.25	789±36	102,000±5,390	414	53,684
34		2.3±0.25	2,420±118	41,900±2,764	1,052	18,217
35		3.1±0.26	57±7.4	76,000±6,810	19	24,516

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.