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National Institutes of Health (September 17, 2012): New Brain Cleaning System Discovered
Scientists have discovered a system that drains waste products from the brain. The finding may reveal ways to treat neurodegenerative disorders like Alzheimer's disease.
Our bodies remove dead blood cells and other waste through a network of vessels called the lymphatic system. The brain, however, has a different method of keeping clean. Cerebrospinal fluid cleanses brain tissue. But how the fluid moves through the brain and clears water wasn't well understood. Until now, scientists could only study brain tissue in animals that were already dead. They thought nutrients and water were transported through the slow process of diffusion.
In a new study, a research team lead by Drs. Jeffrey Iliff and Maiken Nedergaard at the University of Rochester Medical Center used a method called 2-photon laser scanning microscopy to analyze the flow of cerebrospinal fluid in living mouse brains. This new technology allowed the scientists to study the intact brain in real time. They injected tracer molecules into the subarachnoid space, a cerebrospinal fluid-filled cavity between the membranes that cover the brain and spinal cord. their work, funded in part by NIH"s National Institute of Neurological Disorders and Stroke (NINDS), appeared in the August 15, 2012, issue of Science Translational Medicine.
To their surprise, the scientists founds that the tracer molecules flowed along a series of channels surrounding blood vessels. In the brain, blood vessels are surrounded by cells caled astrocytes. These cells have projections called end feet that wrap around arteries and veins like a layer of piping.