Sleepy Dogs Don't Lie: A Genetic Disorder Informative About Sleep
- Molecular Neurobiology Laboratory, SRI International-PDD, Menlo Park, California 94025, USA
This extract was created in the absence of an abstract.
Molecular genetic approaches have facilitated our understanding of numerous diseases and provided important insights into the neurobiological basis of various behaviors. Until recently, the complex behavioral and physiological adaptation known as sleep has been impervious to such approaches. In the last two years, however, a familiar theme has been played out in the sleep field: The discovery of the genetic basis of an animal model of a human disorder has implications both for the treatment of patients and for the neural basis of a specific behavior. In this issue, the paper by Hungs et al. provides the latest chapter in this fascinating and rapidly unfolding story.
Narcolepsy in Humans
Narcolepsy, sometimes called Gélineau's disease after the neurologist who coined the term, was first described more than a century ago (Westphal 1877) and has been of continuing interest because of its unique sleep phenotype. The “narcoleptic tetrad” of symptoms include excessive daytime sleepiness (EDS); cataplexy, a sudden loss of muscle tone during wakefulness usually precipitated by strong emotional stimuli; sleep paralysis, a transient inability to move upon awakening that can persist as long as 15 minutes; and hypnogogic hallucinations, vivid dreamlike imagery at sleep onset that can be quite frightening to a narcoleptic person. The last three symptoms are similar to characteristics of normal rapid eye movement (REM) sleep, a stage of sleep during which dreams are often reported and the voluntary musculature is actively inhibited resulting in muscle atonia. Because of these similarities and the fact that the latency between sleep onset and the first REM period is greatly reduced in narcoleptics, narcolepsy has been thought to be a disorder of REM sleep.
The mode of inheritance of narcolepsy is complex: Although 1%–2% of the first-degree relatives of narcoleptic patients manifest the disorder (compared with 0.02%–0.18% of the general population), the low degree …
