The findings offer new insights both into normal sleep and narcolepsy.
To "dissect" the neurological components of sleep, the scientists studied the phenomenon of cataplexy -- the abrupt loss of muscle tone while maintaining a state of complete wakefulness. The majority of narcoleptics suffer from this malady, in which a strong emotion, even a funny joke, can cause them to drop into a state of paralyzed awareness ranging from a few seconds to half an hour. Similarly, in narcoleptic dogs, emotional excitement, play, or even receiving a favorite food can trigger cataplexy.
The researchers have been using cataplexy as a unique natural "experiment" to distinguish the neural basis of loss of consciousness from that of skeletal muscle paralysis during sleep.
In their studies, they have concentrated on the role of three kinds of neurons in the brain's hypothalamus -- the central controlling region for sleep and wakefulness.
In their previous experiments, they found that noradrenalin- and serotonin-triggered neurons reduced their electrical activity during cataplexy. In the latest experiments, they measured the activity of histamine-triggered neurons when the dogs experienced cataleptic episodes when given a food treat or toy.
The scientists discovered that the histamine-triggered neurons maintained their normal waking-level activity during such cataplexy. What's more, when the researchers administered drugs that increased cataplexy, they found no effect on the histamine neurons. In contrast, a drug that affected the norepinephrine neurons aggravated catap
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Contact: Heidi Hardman
hhardman@cell.com
617-397-2879
Cell Press
26-May-2004