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Scientists identify cells responsible for sleepiness and depression
Medical expert of the article
Last reviewed: 01.07.2025
Scientists have identified a special group of cells in the hypothalamus that are activated in response to light and are capable of keeping the human brain alert and active. These cells produce the neurotransmitter hypocretin, the deficiency of which leads to chronic drowsiness and depressive states.
The human sleep-wake cycle, which is governed by the rising and setting of the sun, is easily disrupted by artificial light. Everyone knows how difficult it is to fall asleep when there is bright light around, and how easy it is to fall asleep in the dark.
Scientists from the University of California (Los Angeles) have discovered a group of cells in the brain whose function is to distinguish light from darkness.
These cells are a group of neurons in the hypothalamus that regulate sleep and the autonomic nervous system, and control body temperature, hunger, and thirst. These cells produce the neurotransmitter hypocretin (orexin). Previous studies have found that hypocretin deficiency leads to the development of narcolepsy and constant drowsiness, and increases the risk of Parkinson's disease.
The experiment, which consisted of studying the behavior of mice with switched-off hypocretin synthesis, was conducted on mice. The results of the study showed that animals with an inactive hypocretin gene were unable to perform tasks in the light, but coped well with them in the dark.
The results of the study lead scientists to the conclusion that hypocretin is something like an energy drink: hypothalamus cells, communicating with each other with the help of this substance, are able to maintain the brain in an active state in response to light. It is these cells that are the reason why it is difficult for us to fall asleep in bright light, and a deficiency of hypocretin leads to constant drowsiness and depression.
In the future, scientists hope to create a drug that could affect the cells that secrete hypocretin and combat drowsiness and depressive states.
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