when neurons start shouting “go to bed NOW!”

DrosophilaA study carried out in fruit flies (2–4 millimetres long Drosophila) by some clever researchers at Oxford University’s Centre for Neural Circuits and Behaviour (CNCB) has recently pointed out a sleep mechanism which is meant to be relevant to humans.

Human sleep regulation is supposed to be managed by two mechanisms:

  • a first one, called body clock, related to the external environment. For instance, thanks to it, humans and others animals get used to the 24-hour day-night cycle and regularly alternate sleep-wake cycles;
  • a second one, related to the body homeostasis, which monitors the internal environment and basically makes us feel spleepy when we’ve been awake for too long. Such mechanism works like a sleep switch and is separate from external factors.

i-am-not-sleepy-and-i-will-not-go-to-bedProfessor Gero Miesenböck, in whose laboratory the research was performed, says that “what makes us go to sleep at night is probably a combination of the two mechanisms. The body clock says it’s the right time, and the sleep switch has built up pressure during a long waking day“. Now, the researchers found (in the tiny Drosophilae’s brains) a group of sleep-promoting neurons that work as a thermostat which automatically turns on when it’s too cold: such neurons are active when the body is tired and needs to sleep, while they don’t fire under fully rested conditions. Doctor Jeffrey Donlea, specialised in testing new scientific ideas in flies at the CNCB, says that “there is a similar group of neurons in a region of the human brain. These neurons are also electrically active during sleep and, like the flies’ cells, are the targets of general anesthetics that put us to sleep“. Therefore, a similar molecular mechanism is likely to operate in humans too. In order to specifically solicit the sleep switch, certain genes were silenced in a group of flies’ brains: a key molecular component was disabled in order to keep the sleep-inducing neurons permanently switched off. The mutant flies were found not to be able to catch up on lost sleep after being kept awake all night. Such behaviour was assumed to be caused by the disabled molecular component, thus identified as a cause of sleep disorder.

Upon further investigation, this study might help the identification of new targets to improve treatments for sleep disorders like insomnia. In the long term, this research work may provide precious hints to find the answer to the big question: “What is the purpose of sleep?“. For the moment, what is sure is that the greatest enemy of sleep is the Internet.


main sources: this and that

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