In 2000, researchers at the UCLA Center for Sleep Research published findings showing that people suffering from narcolepsy, a disorder characterized by uncontrollable periods of deep sleep, had 90 percent fewer neurons containing the neuropeptide hypocretin in their brains than healthy people. The study was the first to show a possible biological cause of the disorder.
Subsequent work by this group and others demonstrated that hypocretin is an arousing chemical that keeps us awake and elevates both mood and alertness; the death of hypocretin cells, the researchers said, helps explain the sleepiness of narcolepsy. But it has remained unclear what kills these cells.
Now the same UCLA team reports that an excess of another brain cell type this one containing histamine may be the cause of the loss of hypocretin cells in human narcoleptics.
UCLA professor of psychiatry Jerome Siegel and colleagues report in the current online edition of the journal Annals of Neurology that people with the disorder have nearly 65 percent more brain cells containing the chemical histamine. Their research suggests that this excess of histamine cells causes the loss of hypocretin cells in human narcoleptics.
Narcolepsy is a chronic disorder of the central nervous system characterized by the brain's inability to control sleepwake cycles. It causes sudden bouts of sleep and is often accompanied by cataplexy, an abrupt loss of voluntary muscle tone that can cause a person to collapse. According to the National Institutes of Health, narcolepsy is thought to affect roughly one in every 3,000 Americans. Currently, there is no cure.
Histamine is a body chemical that works as part of the immune system to kill invading cells. When the immune system goes awry, histamine can act on a person's eyes, nose, throat, lungs, skin or gastrointestinal tract, causing the symptoms of allergy that many people are familiar with. But histamine
|Contact: Mark Wheeler|
University of California - Los Angeles