LONDON (Reuters) - Sleepiness can be controlled by a set of nerve cells in the eye, tests on mice suggest, offering a new target for drug developers that may lead to better sleeping pills, British scientists said on Sunday.
Light levels have long been known to affect alertness, which is why dimly lit rooms lead people to feel drowsy. But the biological mechanism for this has been unclear.
Now University of Oxford researchers have discovered that so-called retinal ganglion cells play a key role. In mice where these cells are turned off genetically, the effects of light on sleep and alertness is completely abolished.
"We have discovered a new pathway that modulates sleep and arousal," lead researcher Russell Foster, of the Nuffield Laboratory of Ophthalmology, said.
"If we can mimic the effect of light pharmacologically, we could turn sleep on and off."
Many drugs have been developed to modify sleep-wake cycles, creating a multibillion-a-year sleeping pill market. But the action of current medicines is relatively crude and the drugs have side-effects.
By targeting the specific mechanism controlling the action of retinal ganglion cells, it may be possible in the future to develop much more sophisticated treatments.
The researchers were able to track the sleep pathway to the brain, showing that two sleep-inducing centers there were directly activated by the cells.
The research, however, is still at an early stage and scientists have yet to establish if the same processes affecting the back-to-front world of the mouse will work in humans.
Because mice are nocturnal, the affects seen in the animal tests were opposite to those that would be expected in humans.
Mice normally sleep when it is light and wake up in the dark -- but those mice in which the light-sensitive cells were turned off stayed wide awake when the lights were on.
The Oxford group's findings were published in the journal Nature Neuroscience.
