"We think that sleep is a function of the body trying to conserve energy in a setting where energetic levels are going down. Our findings suggest that if you were to fast for a day, we would predict you might get sleepy because your energetic stores would be depleted," said study co-author David Raizen, an associate professor of neurology and a member of the Chronobiology and Sleep Institute at Penn.
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Raizen emphasized that while these findings, which were in microscopic worms, "may not translate directly to humans, C. elegans offer a surprisingly good model for studying mammalian slumber. Like all other animals that have nervous systems, they need sleep. But unlike humans, who have complex neural circuitry and are difficult to study, a C. elegans has only 302 neurons — one of which scientists know for certain is a sleep regulator."
To study the link between metabolism and sleep, Science Daily wrote, “the researchers genetically modified C. elegans to ‘turn off’ a neuron that controls sleep. These worms could still eat, breathe, and reproduce, but they lost their ability to sleep. With this neuron turned off, the researchers saw a severe drop in adenosine triphosphate (ATP) levels, which is the body's energy currency. “
"That suggests that sleep is an attempt to conserve energy; it's not actually causing the loss of energy," Raizen explained.
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