Scientists shed light on the brain mechanisms behind a debilitating sleep disorder

Normally muscles contract in order to support the body, but in a rare condition known as cataplexy the body's muscles “fall asleep” and become involuntarily paralyzed. Cataplexy is incapacitating because it leaves the affected individual awake, but either fully or partially paralyzed. It is one of the bizarre symptoms of the sleep disorder called narcolepsy.

“Cataplexy is characterized by muscle paralysis during cognitive awareness, but we didn't understand how this happened until now, said John Peever of the University of Toronto's Department of Cell & Systems Biology. “We have shown that the neuro-degeneration of the brain cells that synthesize the chemical hypocretin causes the noradrenaline system to malfunction. When the norandrenaline system stops working properly, it fails to keep the motor and cognitive systems coupled. This results in cataplexy – the muscles fall asleep but the brain stays awake.”

Peever and Christian Burgess, also of Cell & Systems Biology used hypocretin-knockout mice (mice that experience cataplexy), to demonstate that a dysfunctional relationship between the noradrenaline system and the hypocretin-producing system is behind cataplexy. The research was recently published in the journal Current Biology in September.

The scientists first established that mice experienced sudden loss of muscle tone during cataplectic episodes. They then administered drugs to systematically inhibit or activate a particular subset of adrenergic receptors, the targets of noradrenaline. They were able to reduce the incidence of cataplexy by 90 per cent by activating noradrenaline receptors. In contrast, they found that inhibiting the same receptors increased the incidence of cataplexy by 92 per cent. Their next step was to successfully link how these changes affect the brain cells that directly control muscles.

They found that noradrenaline is responsible for keeping the brain cells (motoneurons) and muscles active. But during cataplexy when muscle tone falls, noradrenaline levels disappear. This forces the muscle to relax and causes paralysis during cataplexy. Peever and Burgess found that restoring noradrenaline pre-empted cataplexy, confirming that the noradrenaline system plays a key role.

CONTACT:

John Peever
Cell & Systems Biology
University of Toronto
Tel: 416-946-5564
Mobile: 647-207-7920
John.peever@utoronto.ca
Kim Luke
Communications, Faculty of Arts & Science
University of Toronto
416-978-4352
Kim.luke@utoronto.ca

Media Contact

Kim Luke EurekAlert!

More Information:

http://www.utoronto.ca

All latest news from the category: Life Sciences and Chemistry

Articles and reports from the Life Sciences and chemistry area deal with applied and basic research into modern biology, chemistry and human medicine.

Valuable information can be found on a range of life sciences fields including bacteriology, biochemistry, bionics, bioinformatics, biophysics, biotechnology, genetics, geobotany, human biology, marine biology, microbiology, molecular biology, cellular biology, zoology, bioinorganic chemistry, microchemistry and environmental chemistry.

Back to home

Comments (0)

Write a comment

Newest articles

Synthetic tissue can repair hearts, muscles, and vocal cords

Scientists from McGill University develop new biomaterial for wound repair. Combining knowledge of chemistry, physics, biology, and engineering, scientists from McGill University develop a biomaterial tough enough to repair the…

Constraining quantum measurement

The quantum world and our everyday world are very different places. In a publication that appeared as the “Editor’s Suggestion” in Physical Review A this week, UvA physicists Jasper van…

Transparent electrodes without the damage

Crucial in the design of any semiconductor device is how to inject and extract an electrical current, and now a KAUST-led team has reviewed ways to do this without damage…

Partners & Sponsors