Comparison between BK and naloxone for induction of functional competence. (A and B) Cultures of peripheral sensory neurons were pretreated with BK (10 μM, 15 minutes), naloxone (1 μM, 3 hours), or a combination of naloxone (3 hours) + BK (15 minutes). Functional competence of MOR (A) and DOR (B) was by measuring DAMGO (1 μM) (A)- or DPDPE (100 nM) (B)-mediated inhibition of PGE2 (1 μM)-stimulated cAMP accumulation as described in Methods. (C and D) Cultures of peripheral sensory neurons were pretreated with BK (10 μM, 15 minutes) or naloxone (1 μM, 3 hours). After pretreatment, concentration response curves to DAMGO (C) or DPDPE (D) were obtained measuring inhibition of PGE2-stimulated cAMP accumulation. Data represent the mean ± S.E.M. of 3 or 4 experiments and are presented as the percentage of the control PGE2-stimulated cAMP levels (for some data points, error bars are contained within the size of the symbol). *P < 0.05, **P < 0.01, ***P < 0.001 compared with the control PGE2-stimulated cAMP levels.