We have all bumped our heads at some point, and such incidents are usually harmless. This is thanks to fluid-filled chambers in our brain that offset minor knocks and jolts and provide padding for sensitive components of our nervous system. Cerebral fluid, however, has more than just a protective function: It removes cellular waste, supplies our nervous tissue with nutrients, and transports important messenger substances. How these messenger substances are actually being delivered to their destination in the brain, however, was unclear until now. Göttingen-based Max Planck researchers have now discovered that tiny cilia on the surface of specialized cells could lead the way. Through synchronized beating movements, they create a complex network of dynamic flows that act like conveyor belts transporting molecular "freight". The results obtained by the scientists suggest that these flows send messenger substances directly to where they are needed. Millions of cilia on the surface of specialized cells inside our body literally make this a hairy affair. Cilia free our airways of dust, mucus, and pathogens, transport egg cells through the fallopian tubes, and help sperm to move forward. The four chambers in our brain, so-called cerebral ventricles, are also lined with a layer of highly specialized cells covered with bundles of cilia on their surface. Although each one is just a few thousandths of a millimeter in size, hundreds of them beating in unison can generate powerful flows.

Gregor Eichele and Regina Faubel at the Max Planck Institute for Biophysical Chemistry, together with Eberhard Bodenschatz and Christian Westendorf at the Max Planck Institute for Dynamics and Self-Organization, have now succeeded in making the complex network of these flows visible in an isolated cerebral ventricle tissue. For their experiments, the researchers in Göttingen concentrated on the third cerebral ventricle, which is embedded in the hypothalamus. "The hypothalamus is a very important control center, regulating functions like the circulatory system, body temperature, sexual behavior, food intake, and hormonal balance. To our surprise, there is a sophisticated transport system to and from the hypothalamus for distributing messenger substances via cerebral fluid," explains Gregor Eichele, Head of the Department of Genes and Behavior at the Max Planck Institute for Biophysical Chemistry.