Magazine article Science News

Sugar May Put You to Sleep: Glucose Triggers Nerve Cells to Spur Drowsiness in Mice

Magazine article Science News

Sugar May Put You to Sleep: Glucose Triggers Nerve Cells to Spur Drowsiness in Mice

Article excerpt

Contrary to parental belief, sugar may actually cause drowsiness, not hyperactivity. Key brain cells awash in glucose put mice to sleep, scientists report in the July 8 Journal of Neuroscience.

"We all experience this strong feeling of sleepiness after a very large meal," says study coauthor Christophe Varin of Lyon Neuroscience Research Center and ESPCI ParisTech in France. Sugar is the reason those postmeal naps are often irresistible, the results suggest.

This study offers hard evidence that sugar promotes sleep, an idea that had been largely anecdotal, says neuroscientist Denis Burdakov of the Francis Crick Institute in London. "It's really great to see it measured properly," he says.

Varin and colleagues injected glucose directly into the brains of mice. Meals, particularly those loaded with carbs, raise sugar levels in the brain, too. This glucose might spur similar brain cells in people to exert sleepy effects.

Scientists already knew that specialized nerve cells in the mouse brain are sleep pushers. These neurons, nestled in the ventrolateral preoptic nucleus, or VLPO, tamp down their sleep-inducing activity in response to various brain messengers that promote wakefulness. The new study shows that glucose has the opposite effect--amping up these sleep-promoting cells.

In the first two hours after glucose was injected directly into the VLPO, mice fell into a deep sleep called slow-wave sleep faster and stayed there longer than mice injected with a nonsugar solution. People and mice spend much of their sleeping time in slow-wave sleep as opposed to more active REM sleep. …

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