Figure 7.

Differential resensitization of DAMGO- and morphine-desensitized MOR receptors. MOR-expressing HEK 293 cells were treated with 10 μM DAMGO or 10 μM morphine for 240 min. Cells were extensively washed and incubated in the absence of agonist for either 0, 10, 20, 30, 40, 50 or 60 min. Cells were then treated with either 25 μM forskolin or 25 μM forskolin plus 0.1 μM etonitazene, and cAMP levels were determined as described under ‘Materials and methods'. The maximum etonitazene-induced inhibition of forskolin-induced cAMP accumulation without agonist preincubation has been defined as 100%. The values represent means±s.e. from three separate measurements performed in duplicate.