Photoreactive compounds developed by scientists of Ludwig-Maximilians-Universitaet (LMU) in Munich directly modulate nerve-cell function, and open new routes to the treatment of neurological diseases, including chronic pain and certain types of visual impairment.
All modes of sensory perception are based on communication between nerve cells. Both the response to the primary stimulus and the transmission of the resulting signal depend on the function of specialized receptor proteins that are associated with the surface membranes of neurons. Many sensory neurons respond only to a single sensory modality, such as mechanical stimulation or temperature. However, Dirk Trauner, Professor of Chemical Biology and Genetics at LMU, has helped develop a method which, in principle, enables all types of neuroreceptors to be controlled by light. "This is achieved by using synthetic molecular compounds that react specifically to light as switches for natural receptors," he says. "The combination results in hybrid photoreceptors, which effectively make the nerve cells that bear them responsive to light. In the long term, we hope to use this approach as the basis for new therapies for neurological disease." Two new studies, on pain receptors and a mouse model for congenital blindness, now report significant advances toward the realization of this goal.
Synthetic opioid as a painkiller
So-called opioids, natural substances related to morphine, have been used as painkillers for thousands of years. The body also synthesizes endogenous opioids, known as endorphins, which bind to the same receptors and have the same analgesic effects as morphine. By chemically modifying the synthetic opioid fentanyl, which is used clinically both as an anesthetic and as an extremely potent painkiller, Trauner and his team have succeeded in conferring photosensitivity on a particular class of opioid receptor. The modified fentanyl retains the ability to bind
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