AsianScientist (Oct. 4, 2017) – Researchers in Japan and China have discovered that the brain region involved in regulating motivation and pleasure also controls sleep. These findings, published in Nature Communications, explain why boredom causes sleepiness.
People often defy sleepiness and stay awake when attention is necessary, but an inescapable desire to fall asleep takes over in boring situations. The brain mechanisms governing the regulation of sleep by cognitive and emotional factors are not well understood.
In this study, researchers at the University of Tsukuba’s International Institute for Integrative Sleep Medicine (WPI-IIIS) and Fudan University’s Department of Pharmacology in the School of Basic Medical Sciences used chemo-genetic and optical techniques to remotely control the activities of nucleus accumbens neurons and the behaviors they mediate. The nucleus accumbens is the part of the brain that is associated with motivation and pleasure.
Interestingly, the researchers found that nucleus accumbens neurons also have an extremely strong ability to induce sleep that is indistinguishable from the major component of natural sleep, known as slow-wave sleep, characterized by slow and high-voltage brain waves.
“The classic sleep-inducing molecule, adenosine, is a strong candidate for evoking the sleep effect in the nucleus accumbens,” said Dr. Yo Oishi at the University of Tsukuba, the lead author of this project.
Adenosine has long been known to represent a state of relative energy deficiency and to induce sleep via adenosine receptors. A specific subtype of adenosine receptors, the A2A receptors, are densely expressed in the nucleus accumbens.
Caffeine, the most widely consumed psychostimulant in the world, produces its arousal effect also in the nucleus accumbens by blocking A2A receptors. Compounds that activate A2A receptors in the nucleus accumbens may open safe therapeutic avenues for treating insomnia which is one of the most common sleep problems, with an estimated prevalence of 10 to 15 percent in the general population and 30 to 60 percent in the older population.
The article can be found at: Oishi et al. (2017) Slow-wave Sleep is Controlled by a Subset of Nucleus Accumbens Core Neurons in Mice.
Source: University of Tsukuba; Photo: Pexels.
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