Scientists find where sleep resides in brain

Updated: Sep 26, 2010, 00:00 AM IST

Washington: American scientists claim to have discovered where sleep resides in the brain.

A team at the Washington State University identified the mechanism that causes the brain to switch from being awake to sleeping -- a finding which is expected to pave the way for the development of new sleep aids and even treatments for strokes and brain injuries.

"We know that brain activity is linked to sleep, but we`ve never known how," said James Krueger, WSU neuroscientist and the lead researcher of the study.

"This gives us a mechanism to link brain activity to sleep. This has not been done before," Krueger was quoted as saying by the National Post.

According to Krueger, the way we sleep goes against what science believed previously. "Our work also emphasises that sleep begins as a local process driven by cell activity."

This view, he said, is in contrast to the current sleep research that views sleep as being imposed upon the brain by sleep regulatory circuits.

"The problem with that view is that despite millions of cases of stroke (brain damage) or intentional lesions to those circuits, a sleepless human or animal has yet to be described (with exception of patients in a coma, which is neither a wake nor sleep state)," he said.

During their research, the scientists found how ATP (adenosine triphosphate) -- the fundamental energy currency of cells -- is released by active brain cells to start the molecular events leading to sleep.

The ATP then binds to a receptor responsible for cell processing and the release of cytokines, small signalling proteins known as Sleep Regulatory Substances (SRSs).

In tests on laboratory mice, the researchers found that when mice were given drugs that stimulate their purine receptors (which assist in the release of SRSs in response to ATP), they fell readily into a deep sleep.

Other mice, given drugs to block their purine receptors, found themselves lying awake at night.

By charting the link between ATP and the sleep regulatory substances, the researchers have found the way in which the brain keeps track of activity and ultimately switches from a waking to a sleeping state.

The study, published in Journal of Applied Physiology, showed that ATP is the signal behind those changes.

The mechanism of chemical transmitters and proteins opens the door to a more detailed understanding of the sleep process and possible targets for drugs and therapies aimed at the costly, debilitating and dangerous problems of fatigue and sleeplessness, the researchers said.

PTI

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