New work involving zebrafish sheds new light on how our need for sleep is regulated by our brain activity.
Why, when we have had an intellectually stimulating day, do we tend to be tired at night and need more sleep?
Until now, scientists thought they had an irrevocable answer: according to them, everything was at stake in our circadian system, that is to say the 24-hour rhythm which is defined by the alternation between daytime wakefulness and sleep. During the night. “We have a pretty good understanding of the circadian system – our built-in 24-hour clock – which times our biological rhythms, including sleep cycles, and we know where in the brain that rhythm is generated,” explains Dr Jason Rihel, of the Cell & Developmental Biology department of University College London (UCL).
He and his team looked at our other sleep-regulating system: the homeostatic system and discovered “that it seems to be determined not only by how long you sleep, but also by the intensity of your activity. brain since the last time you slept”. This new work has just been published in the journal Neuron.
An increase in galanin
To understand what processes in the brain drive the homeostatic regulation of sleep – independent of the time of day – the research team studied the larvae of zebrafish, an animal commonly used in biomedical research due to its quasi transparent and its wake/sleep rhythm similar to that of humans.
First, the researchers stimulated the zebrafish’s brain activity with caffeine. They were able to see that the fish then slept longer after the substance dissipated. According to them, this confirms that the increase in brain activity contributes to an increased need for sleep.
By studying the brain of zebrafish, scientists discovered an area similar to an area of the human brain located in the hypothalamus and known to be active during sleep. Upon closer study, they found the presence of a specific brain signaling molecule called galanin. While this is very active during recovery sleep, it does not play such an important role in regular nighttime sleep.
Another brain stimulation experiment on zebrafish was able to confirm the researchers’ hypothesis: their brain does show an increase in galanin activity during recovery sleep.
Overcome sleep disorders
According to the researchers, this finding that excessive brain activity can increase the need for sleep could explain why people often feel exhausted after a seizure. “Our results could also shed light on how some animals may avoid sleep under certain conditions such as famine or mating season: their brains may be able to minimize brain activity to limit the need for sleep. “, advances Dr. Sabine Reichert, co-author of the study.
The researchers also believe that this discovery could help them understand sleep disorders and conditions that impair sleep, such as Alzheimer’s disease. “We may have identified a good drug target for sleep disorders, because it It might be possible to develop treatments that act on galanin,” concludes Dr. Reichert.
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