Figure 3.

Agonist-mediated internalization of receptors in HEK cells expressing δ, β₂, δ-β₂ (Left) or κ, β₂, κ-β₂ (Right) receptors. Cells were treated with indicated concentrations of etorphine for 60 min at 37°C, stained, and analyzed by ELISA, with the use of anti-Flag and anti-myc antibodies. The mean absorbance without agonist treatment is taken as 100%. The data represent means ± SEM (n = 5–7).