Fig. 3.

Persistence of MOR (A) and DOR (B) functional competence after induction by naloxone. Cultures were incubated with either vehicle (HBSS) or naloxone (1 μM) for 3 hours. After a 0- to 90-minute washout period after naloxone treatment, opioid receptor functional competence was assessed by measuring DAMGO (1 µM)- or DPDPE (100 nM)-mediated inhibition of PGE₂ (1 µM)-stimulated cAMP accumulation. Data are expressed as the percentage of the control PGE₂-stimulated cAMP levels and are the mean ± S.E.M. of 3 experiments. *P < 0.05, **P < 0.01, ***P < 0.001 compared with control PGE2-stimulated cAMP levels.