- Created by: Halcy
- Created on: 07-06-15 13:47
The two main symptoms of narcolepsy are extreme daytime sleeppiness and cataplexy. Cataplexy is the sudden and unexpected loss of muscle tone while awake which can lead to an individual collapsing. It can be triggered by any sort of emotional outburst; whether it be fear, anger or joy. Other symptoms include hallucinations and sleep paralysis.
Research has uncovered a link between hypocretin (sometimes called Orexin) and narcolepsy. Hypocretins play an important role in maintaining wakefulness. Hypocretins affect communications between neurons, particularly messages relating to when the body should be awake or asleep. The number of brain cells containing hypocretin is reduced 85-95% in people with narcolepsy. Reduced levels of hypocretin lead to a reduction in other chemicals that are involved in promoting wakefulness. For example, low levels of hypocretin lead to low levels of norepinephrine - which provokes arousal - and lower levels of histamine which promotes wakefulness. The brain region where the hypocretin cells are located is called the hypothalamus. Scar tissue is present in regions of the hypothalamus where hypocretin cells should be. This suggests that they were there at birth, but died later on. What killed them off, however, is still unknown. The first evidence for the hypocretin explanation comes from narcoleptic dogs, who had a mutation on chromosome 12, wich disrupted the processing of hypocretin. This mutant gene was found to affect the neurons and receptors of hypocretin. This defect means that hypocretin cannot perform its usual function of maintaining wakefulness.
Early research demonstrates that it is possible to breed strands of mice and dogs that are narcoleptic; caused by an abscence of hypocretin or its receptors. These finding were replicated with humans to find that they had low levels of hypocretin in their cerebrospinal fluid. This could be due to the fact that…