Had Enough Sleep? There’s a ‘Switch’ in Our Brains That Wakes Us Up!

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Thursday, 04 August 2016

Scientists have pinpointed a ‘switch’ in our brains that lets us know when we need to sleep and when we need to wake up.

There are two systems that govern our sleep. These are the circadian clock, (this works in response to environmental changes throughout the day) and the sleep homeostat, which we don’t know much about.

The circadian clock is a reaction to night and day, as well as other predictable changes, to make sure we sleep at the appropriate time. But this doesn’t explain why we need to go to sleep at all.

Professor Gero Miesenböck, a researcher from the University of Oxford, said that the explanation is likely to come from learning more about the sleep homeostat, the second sleep controller.

He said that the homeostat monitors something that takes place in the brain during waking hours and we fall asleep when whatever it is it measures hits a particular point. He believes that the system resets while we sleep and then the cycle restarts when we wake up again.

The research team studied the brains of a group of fruit flies to find out more about the sleep homeostat. These creatures were also used about 45 years ago in the pioneering circadian clock studies.

Professor Miesenböck said that mammals have a collection of sleep-promoting cells in their brains that have comparable properties to those the researchers examined in the flies. He said the activity of these cells is stimulated by general anaesthetic and they are electrically active during sleep.

The brain cells, also known as neurons, show the sleep homeostat’s output. If they are silent, the fly is awake and if they were electrically active, the fly is asleep.

Published in the Nature journal, the study explains how scientists used the optogenetics technique to flip the brain cell technology off and on using light pulses. This technique roused by a neurotransmitter called dopamine, which of which higher levels can be found in those have taken psychostimulants like cocaine. This effect was also observed in the flies.

The researchers were able to turn on the fly’s ‘sleep switch’ by increasing levels of dopamine, causing the sleep cells to quieten and the fly to awaken. They found an ion channel (nicknamed ‘Sandman’) inside the sleep-control neurons when they are electrically active. This controls the electrical impulses the brain cells communicate through.

Dopamine causes Sandman to short-circuit the neurons and shut them off, so that the fly wakes up. Professor Miesenböck said that if the cells use the Sandman mechanism to flip between silent and active states and if it can be selectively blocked in the cells, scientists would have a new principle for a hypnotic medication.

Dr Jeff Donlea, lead author of the study, compared the system to a thermostat. He said that instead of turning the heating on when it’s too cold, this system makes us sleep when our tiredness exceeds a certain point.