TABLE 2.

E_max and EC₅₀ values of ligand-modulated [³⁵S]GTPγS binding in CB₁-HEK and CB₁-HEK–CRIP_1a cells

Varying concentrations of the indicated ligands were incubated with membranes prepared from the indicated cell lines in the presence of 10 μM GDP and 0.1 nM [³⁵S]GTPγS, as described in Materials and Methods. E_max and EC₅₀ values were derived from nonlinear regression analysis of ligand concentration-effect curves. Data are mean values ± S.E.M. (n = 3–6). The P values in the rightmost column denote significance of the effect of CRIP_1a overexpression, derived from two-way ANOVA (ligand concentration × cell line) of the concentration effect curves. Values <0.05 are considered significant. Significance of E_max and EC₅₀ values between cell lines were determined by Student’s t test.

	CB1-HEK		CB1-HEK-CRIP1a
Ligand	Emax	EC50	Emax	EC50	P value
	% Stim	nM	% Stim	nM
2-AGE	137.7 ± 9.7a	59.9 ± 3.8	108.2 ± 3.7a,*	104 ± 16	<0.0001
HU210	114.6 ± 5.9a,b	0.04 ± 0.01	96.0 ± 6.1b,§	0.06 ± 0.01	<0.0001
WIN55,212-2	112.7 ± 8.8a,b,c	110 ± 41	79.5 ± 1.7c,*	90.6 ± 6.2	<0.0001
CP55,940	100.0 ± 8.7b,c	48.8 ± 2.2	72.0 ± 2.7c,*	51.4 ± 6.3	<0.0001
MAEA	73.8 ± 6.1c	202 ± 37	73.0 ± 6.0c	255 ± 40	0.4928
Levonantradol	73.7 ± 11.3c	34.2 ± 8.6	72.8 ± 0.5c	19.0 ± 5.2	0.2360
THC	19.6 ± 2.7d	11.5 ± 2.4	20.4 ± 3.1d	8.1 ± 1.2	0.1740
Rimonabant	−12.9 ± 1.5	1.0 ± 0.4	−6.5 ± 1.5*	0.5 ± 0.1	0.0002

^*P < 0.05 different from CB₁-HEK cells. ^§P = 0.05 different from CB₁-HEK cells. ^a–dSignificance of E_max and EC₅₀ values between cell lines were determined by Student's t test. Significant differences between ligand E_max values within each cell line are denoted as follows: ligands without any similar letter designations are P < 0.05 different from each other as determined by one-way ANOVA with posthoc Newman-Keuls test.