Nat Commun: Don't you consider a lunch break? Brain ridge fluid pours into brain at noon to 'clean up', study says

Sleep is an evolutionaryly conservative biological function that helps remove harmful metabolites accumulated by the brain when awake and strengthens memory.
sleep, the brain's "cleaner", cerebrospinal fluid (CSF), increases the movement into the lymphatic system, which promotes waste removal.
, however, it is not clear whether the movement of lymphatic fluid is controlled by circadian rhythms.
, researchers at the University of Rochester Medical Center in New York published a study entitled "Circadian control of brain glymphatic and lymphatic fluid fluid" in the journal Nature Communications on September 2.
that the movement of cerebrospinal fluid is controlled by endomorgenic circadian rhythms and is supported by water channel protein 4 (AQP4).
specifically, the researchers injected fluorescent tracer into the CSF pool of mice anaesthetized at noon or midnight, and circulated for 30 minutes before collecting the brain.
the movement of fluorescent tracer through skull imaging during the cycle.
found that CSF tracer in the brain increased inflow during the day by about 53 percent compared to night.
, the results of a 24-hour anaesthetic in mice with different anaesthetics showed that tracer inflow peaked at noon.
these results showed that the cerebrospinal fluid tracer's lymphatic inflow to the brain showed day-night changes regardless of the state of the anaesthetic, and peaked around noon, when the mice were most likely to fall asleep.
increased lymphatic inflow during the day, the researchers tested whether sober mice showed day-night changes in CSF inflow.
showed no significant difference in total inflow, front and rear distribution, or in different sub-regions of CSF tracer between day and night.
, the authors say, is not surprising because the sober brain has limited lymphatic function.
To test the hypothesis that the inflow of lymphatic CSF tracer during the day was not driven by the light and dark cycle, the researchers placed the mice under continuous light for 10 days and monitored their activity continuously.
results showed an increase in CSF inflow during the rest phase compared to the animal behavioral activity phase, and a significant 55 percent increase in the removal rate of Evans Blue, a small molecule azo dye that spreads freely in the brain and binds closely to albumin in the blood, compared to the active phase of animal behavior.
data suggest that differences in the lymphatic system persist in constant light.
differences in the lymphatic system remained in constant light, the researchers also found that daily changes in cerebrospinal fluid discharge were also controlled by circadian rhythms.
, however, this control was reversed from the inflow changes, with the filling of the lymph at night significantly faster than during the day, when the filling of the lymphatic lymph in the jaws decreased by 46%.
study found that the absence of AQP4 eliminated the day-night difference between lymphatic inflow and lymphatic outflow.
suggests that the circadian rhythm of cerebrospinal fluid distribution is supported by AQP4.
Lymphatic drainage shows changes in circadian rhythms at the end, the authors stress: "Although lymphatic functions, such as shift work, have not yet been studied in the model of circadian rhythms, it has been determined that there has been an increase in neurodegenerative diseases, cardiovascular disease risk, and systemic inflammatory markers among shift workers."
understanding how these rhythms with different time and biological functions interact to affect lymphatic function and lymphatic drain may help prevent diseases associated with circadian rhythm disorders.
, the study tells us that taking a nap can help more "cleaners" get into the brain to clean up trash, and not staying up late can help "cleaners" get that garbage out of the brain and promote long-term brain health.
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