An opioid efficacy switch for reversible optical control of analgesia.

A reversible photoswitchable morphinan agonist enables optical control of MOR signaling with reduced side effects in mice.

• Why it matters: Controlling opioid effects precisely is crucial to minimize dangerous side effects and better understand their mechanisms, but current systemic administration lacks specificity.
• What they did: Researchers developed AM-3, a photoswitchable MOR agonist that changes efficacy with light, and analyzed its binding modes and receptor dynamics in structural studies, testing its effects in mice.
• The result: AM-3 allows reversible, repeatable optical control of pain relief in mice with fewer side effects due to limited brain accumulation and local activation capability.