cell activity of narcolepsy, revealed!
June 02 2005
UCLA/Veterans Affairs neuroscientists
have pinpointed the electrical "signature" of
the brain cells whose loss causes human narcolepsy, and
made the first recordings of their activity. Made in freely
moving rats in waking and across the sleep cycle, these
recordings show hypocretin neurons are active during excitement
generated by positive emotions and by interest in one's
surroundings. The study also reveals that these cells
counteract weakness brought on by positive emotion and
play a key role in maintaining brain alertness.
Human narcolepsy is caused by a loss of
cells in the brain's hypothalamus that contain the protein
hypocretin (also called orexin). This discovery was made
by this same group and colleagues and published in September
2000. In human narcoleptics, cataplexy, a sudden loss
of muscle tone that can cause an individual to fall to
the floor, is triggered by laughter, sexual activity and
related pleasant activities, but not by pain or aversive
situations. In normal humans, a similar weakness accompanies
laughter ("doubling up with laughter") and certain
emotions, but the weakness is limited, never resulting
in cataplexy. The current study reveals the neuronal mechanisms
responsible for maintaining alertness and limiting emotionally
The study explains the persistent sleepiness
of narcolepsy and reveals the existence of a brain system
that is most active during rewarding, positive experiences.
Preliminary work indicates that replacement of the natural
wake-inducing chemical hypocretin can prevent cataplexy
and reverse the sleepiness of narcolepsy.
The senior author is Dr. Jerome Siegel,
professor-in-residence at the UCLA Neuropsychiatric Institute
and chief of neurobiology research at the VA Greater Los
Angeles Healthcare System, Sepulveda.
The research was funded by the National
Institutes of Health and Medical Research Service of the
Department of Veterans Affairs.
Original source: http://www.mydna.com