TABLE 2.

Agonist binding affinities of the dopamine D2 receptor expressed alone or coexpressed with the dopamine D5 receptor

Competition binding experiments using [³H]raclopride were performed in membranes from cells stably transfected with the D2 receptor alone or cotransfected with the D5 receptor. The data represent the means ± S.E.M of six experiments, each performed in duplicate.

	D2R			D2R + D5R
	Fraction	KH	KL	Fraction	KH	KL
		nM	nM		nM	nM
Dopamine	0.291 ± 0.084	256.6 ± 105.3	4836 ± 1612	0.271 ± 0.073	144.0 ± 84.4	4030 ± 1113
Quinpirole	0.293 ± 0.047	13.8 ± 8.7	1196 ± 366	0.253 ± 0.034	25.3 ± 3.4	875.5 ± 270.1

KH, high-affinity constant; KL, low-affinity constant