Glial cells have more tasks than expected and are probably responsible for the intelligence. Image: Wikipedia
Reading Glial cells, the most common type of cell in the brain besides nerve cells, have long been regarded as pure support and supply units for the neurons. In the meantime, however, it has become clear that glial cells are not only involved in higher thought processes, they even coordinate them in many cases. Researchers are therefore increasingly trying to decipher glial cell communication in order to better understand how the brain works and to gain new insights into the development of diseases such as epilepsy, Alzheimer's and schizophrenia. They go through the entire brain and live in close proximity to the nerve cells - the glial cells. Nevertheless, for many years they led a shadowy existence: while the neurons became superstars, to whom the brain researchers ascribed credit for everything from feeling through thinking to acting, the glial cells were considered to be a pure cement substance that holds the nerve cells together, supports them, and supplies them responsible is.

But so slowly the alleged support cells step out of the shadows of their neighbors, reports the magazine "bild der wissenschaft" in its September issue. What's more, "Glial cells are by no means only extras in the brain, but quite central players, " says Christian Steinhäuser, head of the Institute of Cellular Neurosciences at the University of Bonn. He is mainly concerned with the astrocytes, star-shaped brain cells, which represent the most common subtype of glial cells with 80 percent. The fact that their crucial role in the brain has been overlooked for such a long time is not least due to a kind of translation problem: glial cells speak a different language than neurons, so to speak.

For while nerve cells primarily use electrical impulses, astrocytes communicate exclusively via biochemical signals, more precisely, via fluctuations in the concentration of charged calcium particles in their interior. These changes travel from cell to cell as in a La Ola wave in the football stadium, and thus also reach astrocytes located in a remote part of the glacier network.

The trick here: the glial cells not only talk to each other, they also translate their messages for the nerve cells. If the calcium level in an astrocyte increases, it releases the messenger compound glutamate - a neurotransmitter that the nerve cells also use for signal transmission. Glutamate, on the other hand, also glial cells receive information from the neurons. At the same time, they sometimes even seem to fulfill the role of a conductor: "They not only listen to the neurons, they also speak with them and give them instructions, " explains US brain researcher Phil Haydon. display

What the cells have to communicate exactly is still unknown. However, the scientists are already investigating one of the main purposes of the palaver: the glial cells seem to ensure that entire groups of nerve cells synchronize their activities and deliver synchronous impulses - a behavior that electrifies neuroscientists. Because the synchronization of nerve impulses is regarded as the basis of higher cognitive performance such as learning, remembering and even conscious thinking.

The example of someone who drinks a cup of coffee in the restaurant is a "science picture": the feeling of the smooth cup surface, the dark color of the hot drink, the smell of the beans, the bitter taste on the tongue - all of these Sensory impressions are registered and processed in different brain areas. But in order to create the overall impression of "coffee enjoyment", these items must be brought together. This happens as the neurons in the involved areas - probably under the command and controlled by the glial cells - synchronize their activity.

Phil Haydon trusts the astrocytes even more: He and a number of other brain researchers suspect that the glial cells co-decide how intelligent a living thing is. Because the higher the development of an animal, the more astrocytes come to a nerve cell. So there are only 0.17 per nerve cell in the worm, at least 0.5 in the frog and cats have about the same number of neurons and astrocytes. The average person has almost twice as many glia as nerve cells, and the leader, the dolphin, has three astrocytes on each neuron. Whether this thesis can be maintained, Haydon now wants to test experimentally.

The great influence of glial cells, however, also has its downside: If, for example, the astrocytes are so important for brain function, it also makes the prime suspect in the search for the cause of various diseases - depression, Alzheimer's, psychiatric disorders such as phobias and schizophrenia and neuropathic pain. In most cases, scientists have already found clear evidence of involvement or even a key role of glial cells.

However, their involvement in the development of epilepsy, a disease characterized by the spontaneous simultaneous firing of all neurons of a brain area, seems particularly obvious. "Despite very modest progress in recent years, epilepsy research is still almost exclusively concerned with nerve cells, " regrets Christian Steinh user. His recommendation, therefore, is to focus more on glial cells, an advice he will follow in the future as part of a major EU collaborative project.

Ulrich Kraft: "New stars in brain research heaven" bild der wissenschaft 9/2008, p. 20 ddp / - Ilka Lehnen-Beyel

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