A genetically encoded biosensor reveals location bias of opioid drug action
Opioid receptors (ORs) precisely modulate behavior when activated by native peptide ligands but distort behaviors to produce pathology when activated by non-peptide drugs. A fundamental question is how drugs differ from peptides in their actions on target neurons. One way that drugs can differ is by imposing selective effects on the conformational equilibrium of individual ORs. We wondered if drugs can also impose selective effects on the location of OR activation in individual OR-expressing neurons. Here we develop a genetically encoded biosensor that directly localizes ligand-induced activation and deactivation of ORs in living cells, and use it to generate the first real-time map of the spatiotemporal organization of - and {delta}-OR activation in neurons. Peptide agonists produce a characteristic activation pattern initiated in the plasma membrane and propagating to endosomes after receptor internalization. Drugs produce a different activation pattern by uniquely driving OR activation in the somatic Golgi apparatus and extending throughout the dendritic arbor in Golgi outposts. These results demonstrate a new approach to probe the cellular basis of neuromodulation and reveal that drugs profoundly distort the spatiotemporal landscape of neuronal OR activation.