Membrane receptors bind endogenous opioids, but opioids for the treatment of pain can bind receptors inside neurons
Paradigm shift : Opioids for the treatment of pain bind to receptors inside neurons - brain science news

While convential wisdom states that molecules bind to receptors on the cell membrane, i.e. on the outside of the cell, a new biosensor has revealed that opioids used to treat pain bind to receptors inside neurons. These receptors were found in endosomes and the Golgi apparatus, and were not activated by endogenous opioids (that is, those that are produced by our own neurons). This surprising finding might help to find new molecular targets for developing safer pain medications, without side effects that may occur by activating the extracellular opioid receptors.

Read the full story: National Institute on Drug Abuse
Scientific publication: Neuron