Sleep Washes Toxins out of the Brain

Sleep Washes Toxins Out of Brain

People have been wondering for centuries just why it is that we sleep and scientists may now have found at least part of the answer.  It could that sleep is literally washing built up toxins out of your brain while you rest.

Scientists say that the brain has a sort of “plumbing system,” called the glymphatic system, which opens up while we sleep, allowing fluid to flow rapidly through the brain.  And, it could be that this system’s purpose is to cleanse the brain of any toxic molecules which have built up during the day.

The scientists have named this network of openings the glymphatic system because it resembles another cleaning system in the body called the lymphatic system.   The letter g was added to the front of the word because it is helped by glial cells, which control the flow of fluids through it, either by shrinking or swelling as needed.

At first, the team studied this unique system by injecting dye into the cerebrospinal fluid of mice while the animals were awake, watching to see how much brain electrical activity occurred.  During this period, there was very little flow of fluid into these spaces.

Then, they tested the mice when they were asleep or put under anesthesia; and, what they found was surprising.  The spaces inside the system expanded by 60 percent, allowing the dye to flow rapidly through them.

Because of this behavior, the scientists hypothesized that the purpose of the network of spaces might be to act as a cleaning system for the brain, washing toxic wastes away from delicate brain tissues while we sleep.

To test whether the glymphatic system was indeed responsible for clearing out toxins during sleep, the scientists injected the mice with labeled beta-amyloid, a protein which is associated with Alzheimer’s disease.  They then measured how long it took for the marked protein molecules to leave the brain while the animals were both awake and asleep.

What they found was that the beta-amyloid disappeared from the brain faster when the mice were asleep, seeming to indicate that sleep is a time when the brain washes out toxins.

The results of this study could have implications in treating several different neurological disorders, the authors say, including Alzheimer’s disease.  It could be, they speculate, that the abnormal buildup of beta-amyloid seen in this condition is caused by a malfunctioning glymphatic system.  And, if this is proven to be true, it could open new pathways for preventing, or maybe even reversing, this devastating neurological disease.  For example, scientists might be able to develop drug therapies which allow for a more efficient flow of cleansing fluid through the system, preventing a damaging build up of toxins.

The study, which was led by Dr. Maiken Nedergaard, who is co-director of the Center for Translational Neuromedicine at the University of Rochester Medical Center, was published on October 18, 2013 in the journal Science.

Written by:  Nancy Schimelpfening


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