The neurotransmitter hypocretin
Hypocretin is a neuropeptide that play an important role in sleep and arousal states. Cell bodies that produce hypocretin are specific to the hypothalamus. The hypocretin system plays an immensely important role in narcolepsy.
Patients who have narcolepsy with cataplexy, which is about 70% of those diagnosed with the disorder, show little to no hypocretin in their CSF. Autopsy of these patients show a significant loss of hypocretin brain cells. Patients who do not have cataplexy associated with their narcolepsy have normal hypocretin CSF levels, but show a dramatically reduced number of hypocretin brain cells. The loss of hypocretin neurons causes a disturbance in transitioning between wakefulness and sleep, which is one proposed explanation for the sleepiness and REM intrusion found in narcolepsy. Currently, we do not know what causes the loss of brain cells, but research shows that it is most likely autoimmune in nature. This means that the body's immune system selectively attacks brain cells that produce and contain hypocretin. More studies are in progress to discover more about this process. |
This diagram of the brain shows the specific location of orexin neurons in the hypothalamus. It also shows the CNS nuclei for wakefulness and the associated neurotransmitters generated by these nuclei.
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Ebrahim, E. O. "The Hypocretin/orexin System." J R Soc Med 95.5 (2002): n. pag. Web.
Hypocretin. Digital image. How Sleep Works. N.p., n.d. Web.
Hypocretin. Digital image. How Sleep Works. N.p., n.d. Web.