If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.


Biological Chemistry

Photoswitch Molecule Controls Pain

Lidocaine-based compound turns pain-sensing neurons on and off when activated via different wavelengths of light

by Lauren K. Wolf
February 27, 2012 | A version of this story appeared in Volume 90, Issue 9

A light-activated compound that resembles the anesthetic lidocaine might lead the way to future pain therapy, according to a report (Nat. Methods, DOI: 10.1038/nmeth.1897). Anesthetics typically suppress pain, but they take a while to wear off and are indiscriminate in which nerve cells they inhibit. Now, Richard H. Kramer of the University of California, Berkeley; Dirk Trauner of the University of Munich; and coworkers have developed a photoswitchable compound that targets specific neurons and can be turned on and off at will. They demonstrated that the lidocaine-like molecule, quaternary ammonium-azobenzene-quaternary ammonium (QAQ), blocks ion channels in pain-sensing nerve cells when in its trans form. After exposure to 380-nm light, QAQ switches to its cis form, unblocking the channels and allowing the neurons to transmit pain signals. The researchers regenerated trans-QAQ with 500-nm light. When applied to the eyes of mice along with the chili-pepper compound capsaicin, trans-QAQ slipped into the rodents’ nerve cells through the protein receptor TRPV1 and lessened the critters’ response to pain. Fiber-optic systems will be needed to use compounds like QAQ inside humans, the scientists say, but meanwhile these photoswitches can help map pain circuitry in the body.


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.