Brain's energy restored during sleep, suggests animal study

Jun 29, 2010
Levels of adenosine triphosphate (ATP), the energy currency of cells, in rats increased in four key brain regions normally active during wakefulness. Shown here is the energy surge measured in the frontal cortex, a brain region associated with higher-level thinking. Credit: Courtesy, with permission: Dworak et al. The Journal of Neuroscience 2010.

In the initial stages of sleep, energy levels increase dramatically in brain regions found to be active during waking hours, according to new research in the June 30 issue of the Journal of Neuroscience. These results suggest that a surge of cellular energy may replenish brain processes needed to function normally while awake.

A good night's rest has clear restorative benefits, but evidence of the actual biological processes that occur during sleep has been elusive. Radhika Basheer, PhD, and Robert McCarley, MD, of Boston V.A. Healthcare System and Harvard Medical School, proposed that levels are key to nightly restoration.

"Our finding bears on one of the perennial conundrums in biology: the function of sleep," Basheer said. "Somewhat surprisingly, there have been no modern-era studies of brain energy using the most sensitive measurements."

The authors measured levels of adenosine triphosphate (ATP), the energy currency of cells, in rats. They found that ATP levels in four key normally active during wakefulness increased when the rats were in non-REM sleep, but were accompanied by an overall decrease in . When the animals were awake, ATP levels were steady. When the rats were gently nudged to stay awake three or six hours past their normal sleep times, there was no increase in ATP.

The authors conclude that sleep is necessary for this ATP energy surge, as keeping the rats awake prevented the surge. The energy increase may then power restorative processes absent during , because consume large amounts of energy just performing daily waking functions.

"This research provides intriguing evidence that a sleep-dependent energy surge is needed to facilitate the restorative biosynthetic processes," said Robert Greene, MD, PhD, of the University of Texas Southwestern, a sleep expert who was unaffiliated with the study. He observed that questions arise from the findings, such as the specific cause of the ATP surge. "The authors propose that the surge is related to decreases in brain cell activity during sleep, but it may be due to many other factors as well, including cellular signaling in the brain," he said.

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zevkirsh
not rated yet Jun 29, 2010
i would bet on the glial cells playing a large role in sleep.
Ronan
5 / 5 (1) Jun 30, 2010
Amazing. One would have thought that something like this would have been uncovered years ago--ATP is, after all, just a LITTLE important to cells, and one would have thought that its levels during sleep would have been measured before--but always new things to discover, I guess. It'll be interesting to hear what comes of this.

...On a side note, though...Hrm. I don't know what lab practices are nowadays, but I've read that some past experiments on sleep done on rats were just a little on the horrific side. Hopefully, however this is explored the exploration doesn't involve things like forcing rats to stay awake until they die of sleeplessness and so on.
chewi
not rated yet Jun 30, 2010
I wonder if this knowledge could be used to stave off the effects of sleep deprivation? Find out how to juice up the brain with ATP ... time to start planning the next energy drink :)

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