(A) N18TG2 WT, empty vector (Control), CRIP1a XS, and CRIP1a KD cells were serum-starved for 16 h, pretreated for 2 h with 1 μM THL, and quantitated for non-ligand mediated CB1R constitutive phosphoERK1/2 using the In-cell-Western assay as described in Materials and Methods. To determine phosphoERK levels the ratio of immunoreactive phosphoERK:ERK was calculated for each individual clone and compared to WT set as 100%. (B) Cells were serum-starved for 16 h, pretreated for 2 h with 1 μM THL, and treated with either vehicle or 10 nM of the CB1R antagonist SR141716A for 5 min. PhosphoERK1/2 was calculated as the ratio of phosphoERK1/2 to total ERK, and compared to WT basal levels, set as 100%. Data are expressed as the mean ± S.E.M. from four independent experiments performed in duplicate. & p<0.05 indicates significantly different from vehicle, and *p<0.05 indicates significantly different from WT using one-way ANOVA and Dunnett’s post-hoc test.