TABLE 1.

Affinity of D₄-selective ligands for the wild-type D₂ and D₂-V2.61(91)F mutant receptors expressed in COS-7 cells Affinities for the wild-type D₄ receptor are shown for comparison. Affinity values (K_i or K_D, nanomolar) are expressed as geometric averages of the mean of three experiments ± S.D. The fold changes in affinity values relative to the wild-type D₂ (D₂-WT) are shown in parentheses with the direction of the change indicated by arrows: ↑, increase in K_i value corresponding to a decreased affinity; and ↓, decrease in K_i value corresponding to an increased affinity.

Ligand	Structure	D2-WT	D2-V2.61(91)F	D4-WT
L-745,870 (CPPMA)		656 ± 227 (1)	482 ± 251 (↓ 1.4)	0.32 ± 0.14 (↓ 2050)
L-750,667c		1400 ± 950 (1)	1100 ± 510 (↓ 1.3)	0.11 ± 0.02a (↓ 13,400)
RBI-257		85 ± 12 (1)	78 ± 3.3 (↑ 1.1)	0.27 ± 0.10b (↓ 315)
FAUC213c		1300 ± 640 (1)	1200 ± 730 (↓ 1.1)	1.1 ± 0.22b (↓ 1030)
Ro61-6270		655 ± 274 (1)	1121 ± 70* (↑ 1.7)	0.89 ± 0.12b (↓ 736)
NGD 94-1		817 ± 284 (1)	3358 ± 266* (↑ 3.3)	0.3 ± 0.04b (↓ 2720)
PD168,077		1380 ± 64 (1)	3601 ± 474*(↑ 2.6)	1.5 ± 0.41b (↓ 540)
(—)-Quinpirole		812 ± 617 (1)	673 ± 466 (↓ 1.2)	N.D.
[3H]Methylspiperone		0.016 ± 0.0032 (1)	0.066 ± 0.030* (↑ 4.1)	0.29 ± 0.030a (↑ 18)

N.D., not determined

^*Significant differences between values for wild-type D₂ and D₂-V2.61(91)F mutant receptors were determined at 95% confidence by Dunnett's multiple comparison test

^aSchetz et al. (2000)

^bKortagere et al. (2004)

^cFloresca et al. (2005)