The effect of co-expression of GRK2 and subsequent treatment with β-funaltrexamine on the potency and intrinsic activity of µ-opioid receptor agonists in a β-arrestin recruitment assay.

Functional properties of agonists in the β-arrestin assay were determined as described in the experimental section. Potency values before and after treatment with β-funaltrexamine are expressed as pEC50±s.e.m (EC50 nM). Emax values before β-funaltrexamine treatment are expressed as % of the maximal response of DAMGO in U2OS µ-opioid receptor β-arrestin cells co-expressing either GFP or GRK2 (mean±s.e.m). The percentage reduction in Emax after treatment is expressed as a percentage of the agonist's Emax before treatment (mean±s.e.m). Data are from four independent experiments.
AValues are significantly different from those determined in the absence of GRK2 (p<0.05, two-tailed t-test).