FIGURE 4.

DIM is a weak CB₁ inverse agonist. Response of the human CB₁ receptor to the test molecules in the β-arrestin assay (A), radioligand competition binding assay (B), GTPγS binding assay (C), and cAMP assay (D). ○, CP55940; □, DIM; ▴, 2-AG; ▾, anandamide; and ♦, arachidonic acid. A, HEK293-BAEA parental cells were transiently transfected with CB₁ and then assayed the next day. B and C, membrane preparations from a CB₁-CHO stable cell line were used. D, CB₁-CHO stable cell line was seeded and 16 h later stimulated with test compounds along with 60 μm of forskolin. After 30 min of stimulation, cells were lysed, and cAMP level was measured using cAMP-HTRF HighRange kit. The y axis plots the FRET ratio that is inversely proportional to the cellular cAMP concentration.