Special brain cells trigger urge to sleep

Brain cells called astrocytes trigger the urge to sleep that comes with prolonged wakefulness, according to a study based on mice.

These cells release adenosine, a chemical known to have sleep-inducing effects that are inhibited by caffeine.

“This research could lead to better drugs for inducing sleep when it is needed, and for staving off sleep when it is dangerous,” said Merrill Mitler, programme director, National Institute of Neurological Disorders and Stroke (NINDS).

Michael Halassa and Philip Haydon, Tufts University School of Medicine in Boston and Marcos Frank and Ted Abel, University of Pennsylvania School of Medicine, Philadelphia, collaborated on the project.

As the waking hours tick by, all animals experience an increasing urge to sleep, known as sleep pressure. If sleep is delayed, a deep, long sleep usually follows as the body’s means of compensating.

Prior studies pointed to adenosine as a trigger for sleep pressure. The chemical accumulates in the brain during waking hours, eventually helping to stimulate the unique patterns of brain activity that occur during sleep.

The results of the new study show that “adenosine from astrocytes clearly regulates sleep pressure”. He noted that this is the first time a non-neuronal cell within the brain has been shown to influence behaviour. The study appeared in the journal Neuron.

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