TABLE 1

Evidence for functionally selective CB₂ ligands

Cannabinoid ligands from multiple classes were tested for their abilities to activate ERK1/2 MAPK in rCB₂-expressing HEK293 cells, promote β-arrestin₂ membrane recruitment in HEK293 cells transiently transfected with rCB₂ and β-arrestin₂-mRFP, and inhibit VGCCs in mCB₂-expressing AtT20 cells. Positive values reflect inhibition of VGCCs and negative values reflect activation (e.g., inverse agonism). Protocols for each experiment were identical to those done in Figs. 4 to 6. Data for ERK1/2 and VGCC experiments were analyzed using unpaired Student's t test vs. native HEK293 or native AtT20 cells, respectively. Data for β-arrestin were analyzed using one-way ANOVA with Dunnett post-tests. Data for internalization from Figs. 1 and 2 and binding data obtained from the cited references are included for additional comparison. Drug concentrations: 10 μM 2-AG was used for internalization (n = 12), and 5 μM 2-AG was used for MAPK activation (n = 6–15), β-arrestin recruitment (n = 5–15), and VGCC inhibition (n = 4–17). All other drugs, 1 μM. Values without symbols are not statistically significant.

Drug	Internalization	MAPK Activation	β-Arrestin Recruitment	VGCC Inhibition	CB₂K_i
	% basal		membrane/cytosol ratio	% inhibition	nM
CP55,940	61 ± 1.9	130 ± 3.6^***	1.9 ± 0.11^{^†††}	17 ± 2.4^**	0.64–2.8^{^a}
WIN55,212–2	100 ± 3.2	130 ± 4.9^**	1.1 ± 0.035	−3.4 ± 3.2	0.28–16.2^{^a}
AM1241	100 ± 6.6	100 ± 3.5	1.0 ± 0.056	−0.83 ± 1.1	3.4^{^b}
JWH015	91 ± 5.8	120 ± 2.4^***	1.1 ± 0.030	−3.9 ± 2.1^*	14–430^{^a}
JWH133	77 ± 3.3	120 ± 2.7^***	1.2 ± 0.058^{^†††}	18 ± 6.2^*	3.4^{^a}
THC	100 ± 2.0	120 ± 2.2^***	1.1 ± 0.058	−7.0 ± 2.7	1.7–75^{^a}
THCV	88 ± 2.0	120 ± 2.1^**	1.0 ± 0.032	−17 ± 7.4	63–75^{^c}
AM1710	71 ± 3.0	120 ± 3.2^**	1.3 ± 0.060^{^†††}	−3.1 ± 4.1	6.7^{^d}
A-836339	82 ± 2.1	120 ± 2.5^***	1.2 ± 0.039^{^††}	16 ± 4.1	0.64^{^e}
2-AG	81 ± 6.3	130 ± 8.1^*	1.1 ± 0.025	33 ± 6.2^*	140–1400^{^a}
GW405833	N.D.	N.D.	N.D.	−2.5 ± 1.4	12^{^f}
AM630	100 ± 2.1	97 ± 1.3	1.0 ± 0.022	−12 ± 2.4^**	31^{^a}
SR144528	130 ± 4.5	99 ± 2.0	0.93 ± 0.039	−10 ± 3.2^*	0.040–15^{^a}

N.D., no data (GW405833 not tested in control cells).
↵* p < 0.05 versus untransfected control cells.
↵** p < 0.01 versus untransfected control cells.
↵*** p < 0.001 versus untransfected control cells.
↵†† p < 0.01 versus untreated control.
↵††† p < 0.001, versus untreated control.
↵a Miller and Stella, 2008.
↵b Ibrahim et al., 2003.
↵c Thomas et al., 2005.
↵d Khanolkar et al., 2007.
↵e Yao et al., 2009.
↵f Gallant et al., 1996.