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Last Updated: Tuesday, 16 March, 2004, 03:25 GMT
Brain chemical helps narcolepsy
Man asleep
People with narcolepsy experience an uncontrollable need to sleep
A chemical found naturally in the brain could be used to treat the sleep disorder narcolepsy, US scientists say.

Researchers at the University of Texas said injecting a chemical called orexin stopped symptoms in mice with narcolepsy.

They found the treatment made the mice more alert and reduced other narcoleptic symptoms, such as muscle weakness, called cataplexy.

The study appeared in the Proceedings of the National Academy Sciences.

Dr Masashi Yanagisawa, professor of molecular genetics, and colleagues studied genetically modified mice which lacked the ability to naturally produce orexin.

Orexin are small chains of molecules, produced by nerve cells in the area of the brain called the hypothalamus.

No rebound sleep

It is thought that people with narcolepsy are unable to produce this chemical, due to cells in the brain that produce it being damaged.

The researchers injected the modified mice with orexin peptides. They found it increased wakefulness, regular sleep patterns and stopped cataplectic fits.

Furthermore, the treatment did not cause 'rebound sleep', a common side-effect of amphetamine treatments where the person needs to regain sleep lost while awake on the drug.

Symptoms of narcolepsy
Excessive sleepiness: an uncontrollable need to sleep during the day
Cataplexy: a sudden loss of muscular control, often triggered by an emotional event
Sleep paralysis, where the person is unable to move or speak when falling asleep or waking up
Hyponagogic Hallucinations, where the person thinks the dream is reality

"This is extremely important because it shows that these mice retain the ability to respond to orexin," Dr Yanagisawa said.

"Our experiments provide a strong proof of concept that introducing into the brain a molecule that mimics the effect of orexin will be the fundamental cure for narcolepsy."

He said new therapies could be developed from orexin receptor agonists, which mimic the effect of orexin.

He said the drug could also play a role in treating people with insomnia, to help them stay awake during the day.

Dr Adrian Williams, director of Sleep Disorder Centre at of Lane-Fox Unit, St Thomas's Hospital London said the new study is significant and could provide a better alternative to current treatments, which are mostly amphetamine based.

One of the most commonly used drugs in the UK to treat narcolepsy is dexamphetamine sulphate, or Dexedrine.

"We've measured orexin in humans with narcolepsy and found they don't seem to have it- or have undetectable levels of it.

"This new treatment is likely to be better, although current treatments are not curative, and it is unlikely that orexin would be curative," he told BBC News Online.

"This is probably five to ten years off being developed in a form that can be given to humans. "

He said around 30,000 people in the UK suffer from narcolepsy.




SEE ALSO:
Sleep master chemical found
16 Jan 03  |  Health
Breakthrough on narcolepsy
31 Dec 99  |  Health


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