Controlling sleepiness

21 August 2008

A set of nerve cells in the eye controls our levels of sleepiness according to the brightness of our surroundings, University of Oxford researchers have discovered.

In the study, supported by Wellcome Trust and European Commission funding, the researchers showed that retinal ganglion cells directly regulate the activity of sleep centres in the brain, providing a new target for the development of drugs to control sleep and alertness.

“We have discovered a new pathway that modulates sleep and arousal,” says Professor Russell G Foster of the Nuffield Laboratory of Ophthalmology. “If we can mimic the effect of light pharmacologically, we could turn sleep on and off.”

Professor Foster and colleagues have previously shown that the eye contains a group of retinal nerve cells that are sensitive to light. Working on mouse models in which these retinal ganglion cells have been turned off genetically, the research team found that the effects of light on sleep and alertness were completely abolished.

The researchers were able to track this sleep pathway to the brain, where two sleep inducing centres are directly activated by the cells, turning sleep on or off.

Lupi D et al. The acute light-induction of sleep is mediated by OPN4-based photoreception. Nat Neurosci 2008 [Epub ahead of print].