HEK293 cells were transfected with eCB2.0 DNA plasmid and changes in fluorescent signal measured by high-throughput fluorescence assay. A] Comparison of GRABeCB2.0 activation kinetics elicited by each ligand at a concentration that approaches their respective EC50s. Shaded areas in time courses and error bars represent s.e.m. B] Comparison of the EC50 of each ligand and their corresponding end response at a concentration that approached their respective EC50 and measured between 3–5 min. Y axis positive value represent increase in fluorescent signal (i.e., AEA, CP and D9-THC) and negative values represent decrease in fluorescent signal (i.e., 2-AG, 1-AG, 2-LG and 2-OG). C] Comparison of the maximum increase in GRABeCB2.0 fluorescent signal as expressed by area under the curve and as a percent of 3 μM 2-AG produced by each ligand. D-F] Antagonism of each response by SR1 (100 and 300 nM).