Orexin Cures Narcolepsy, Study Shows

Researchers have identified a link between narcolepsy and a chemical that serves as a brain messenger. The study involved giving narcoleptic mice the neurotransmitter orexin. The mice that had been previously stripped of their ability to produce the chemical were cured of the disease. Orexin is produced by neurons in the hypothalamus region of the brain. Earlier research had shown that, when the orexin gene is disrupted or orexin-producing neurons are eliminated, mice show symptoms of narcolepsy.

For this latest study, the researchers injected orexin peptides into the brains of mice that could not produce the chemical on their own.The injections worked by increasing wakefulness and reducing episodes of muscle weakness. Also, no "rebound sleep" was detected, which often occurs after drugs such as amphetamines are used to offset the symptoms of narcolepsy. These findings were reported in the Proceedings of the National Academy of Sciences (March 15, 2004).

Although the findings still need to be tested on humans, researcher Masashi Yanagisawa, MD, PhD, said, "Now it's very well proven that the vast majority of human patients do have orexin deficiency, just like mice."