TABLE 4

β arrestin-2 recruitment induced by dopamine and norepinephrine mediated by D2LR, D2SR, D3R, D4.2R, D4.4R, and D4.7R

Results were obtained from β arrestin-2 recruitment-BRET experiments in HEK-293T cells transiently transfected with different D₂-like receptors fused to RLuc8 and β arrestin-2 fused to mVenus. Data of individual experiments were fit by nonlinear regression to a sigmoidal dose–response relationship against the agonist concentration. The EC₅₀ and E_max values are the mean ± S.E.M. of 5 to 15 experiments performed in triplicate. E_max values are expressed as 1000 × [BRET_max − BRET_basal].

Receptor	Dopamine		Norepinephrine		NE/DA (EC₅₀)
Receptor	EC₅₀ (nM)	E_max	EC₅₀ (nM)	E_max	NE/DA (EC₅₀)
D2LR	96 ± 16	11 ± 1	4800 ± 1720	11 ± 2	50
D2SR	105 ± 21	18 ± 2^{^a}	2880 ± 1150	17 ± 2	27.4
D3R	3 ± 1^{^b}	15 ± 2^{^c}	32 ± 5^{^c}	13 ± 2	10.7
D4.2R	38 ± 13^{^c}	9 ± 1	3750 ± 1620	10 ± 2	100
D4.4R	66 ± 13	8 ± 1	2830 ± 666	7 ± 1	43
D4.7R	44 ± 12^{^c}	9 ± 1	1840 ± 889	8 ± 2	41.8

NE/DA, ratio between EC₅₀ values of norepinephrine and dopamine for each receptor.
↵^a P < 0.01, compared with D2LR (one-way analysis of variance, followed by post hoc Newman-Keuls test).
↵^b P < 0.001, compared with D2LR (one-way analysis of variance, followed by post hoc Newman-Keuls test).
↵^c P < 0.05, compared with D2LR (one-way analysis of variance, followed by post hoc Newman-Keuls test).