Narcolepsy affects the systems in the brain that help us stay awake. Normally, alerting signals come from the brain stem, a region deep in the brain responsible for many basic functions. These signals spread out and “wake up” the rest of the brain. Meanwhile, a cluster of cells in another nearby region called the hypothalamus produce the chemical hypocretin. Hypocretin activates and maintains the action of those alerting signals coming from the brain stem.
In a person with narcolepsy, the cells in this specialized region of the hypothalamus have died off. Even though it’s a relatively small cluster of cells, the impact on waking and sleep is dramatic. Without hypocretin, it’s hard for a person to stay awake for long periods of time, and they experience overlaps between waking and sleep—such as vivid hallucinations and paralysis when falling asleep or waking up.
The loss of hypocretin also affects the action of other key chemicals in the brain, such as dopamine, serotonin, and norepinephrine. This is why antidepressants (which act on these neurotransmitters) are sometimes prescribed for narcolepsy.
Scientists are working on ways to target and stimulate hypocretin receptors, as a way to mimic the presence of the chemical. They are also working on understanding how hypocretin cells are lost in the first place (the autoimmune response) so they can target the first stage of the process and halt the development of narcolepsy symptoms.