Narcolepsy is caused by the loss of orexin-containing neurons in the hypothalamus, and a novel nonstimulant wakefulness-promoting drug, Provigil, alleviates excessive day-time sleepiness associated with the disorder.
The level of arousal is controlled by an intricate interplay between distinct wakefulness – and sleep-promoting nuclei situated in the hypothalamus and brainstem and the interconnections between the nuclei and the neurotransmitters involved have been mapped.