Table 5

Antagonism of dopamine-stimulated [³⁵S]GTPγS binding to CHO-hD₂ and -hD₃ membranes

Antagonist	hD₂		hD₃		K_BRatio hD₂/hD₃
Antagonist	pK_B	K_B	pK_B	K_B	K_BRatio hD₂/hD₃
		nM		nM
Haloperidol	9.30 ± 0.13	0.50	7.67 ± 0.27	21.3	0.02
S 14297	6.56 ± 0.09	275	7.53 ± 0.08	29.5	9.3
GR 218231	7.17 ± 0.16	67.6	8.65 ± 0.03	2.23	30

Antagonist potencies (pK_B values) were calculated from IC₅₀ values for inhibition of dopamine (3 μM for hD₂, 1 μM for hD₃)-stimulated [³⁵S]GTPγS binding. pK_B values are expressed as means ± S.E. of mean of at least three independent experiments.K_B values were calculated from mean pK_B values.