The sleep of mammals including humans consists of REM sleep and non-REM sleep, and dreams occur actively during REM sleep (about 80% of total human sleep time is non-REM sleep and about 20% is REM sleep).So far, it has been suggested that the hormonal environment during non-REM sleep contributes to the recovery of the body, but the contribution of REM sleep to the recovery of the brain and body has been a mystery.

　The exchange of substances, which delivers the oxygen and nutrients in the blood necessary for the brain and collects unnecessary carbon dioxide and waste products, is carried out through capillaries.The research group established a technique to directly observe the microenvironment in the mouse brain using a special microscope (two-photon excitation microscope), and observed the flow of red blood cells in the capillaries in the sleeping mouse brain. ..

　As a result, it was found that the influx of red blood cells into the capillaries of the cerebral cortex increased significantly (nearly twice) during REM sleep.It is thought that the brain is refreshed by active substance exchange in the cerebral cortex during REM sleep.A low rate of REM sleep in adults increases the risk of developing dementia, etc., but lack of REM sleep impairs active substance exchange in the cerebral cortex during REM sleep, which may be involved in the development of dementia. There is sex.The study also found the importance of adenosine receptors, which are also target substances for caffeine, in increasing blood flow in capillaries during REM sleep.

　It is expected that the results of this research will lead to an understanding of the mechanism of the onset of dementia and contribute to the development of a completely new treatment method targeting REM sleep.

Paper information:[Cell Reports] Cerebral capillary blood flow upsurge during REM sleep is mediated by A2a receptors