Figure 5. The ability of ligands to activate G proteins through the µ-opioid receptor.

Agonist stimulated [³⁵S]GTPγS binding to membranes prepared from U2OS µ-opioid receptor β-arrestin cells in the absence (A) and presence (B) of co-expressed GRK2 was measured. Concentration-effect curves ligands were determined as described in the experimental system. Graphs are representative of four independent experiments.