Research Press Release

A light-switch to turn off pain

Nature Methods

February 20, 2012

A molecule that can be turned on or off to block the activity of pain-sensing neurons in rats is reported online this week in Nature Methods. These findings have potential value as both scientific and clinical tools for controlling pain sensation. Local anesthetics suppress pain sensation by blocking the activity of pain-sensing neurons, but most of these compounds act nonselectively on all nervous-system cells. Some compounds act preferentially on pain-sensing neurons, but their actions persist for many hours. To develop a molecule that can block the activity of pain-sensing neurons in a controlled and reversible manner, Richard H. Kramer and Dirk Trauner synthesized a molecule, named QAQ, that is structurally similar to a previously used lidocaine derivate. It uses the same mechanism to selectively enter pain-sensing neurons, but its activity can be controlled by light. QAQ switches between two conformations in response to different colors of light, and only one of them has a pain-suppressing effect—ultraviolet light turns it on and green light turns it off. The authors show the capacity of QAQ as a light-sensitive analgesic in the retina of living rats.


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