Endocytic profiles of δ-opioid receptor ligands determine the duration of rapid but not sustained cAMP responses.

Traditional assays that monitor cAMP inhibition by opioid receptor ligands require second-messenger accumulation over periods of 10-20 minutes. Since receptor regulation occurs within a similar time frame, such assays do not discriminate the actual signal from its modulation. Here we used bioluminescence resonance energy transfer to monitor inhibition of… (More)