Scientists for the first time have documented a newly understood pathway for transmitting signals within the brain, according research published online Nov. 9 in the journal Nature. The study showed the connection in the living tissue of fruit flies, but the results suggest human glial cells could be targeted for therapeutic medication regulating everything from hunger to mood.
“This has profound implications and opens up a whole other way for thinking about these cells,” said co-author Marc Freeman, Ph.D., director and senior scientist with the Vollum Institute at OHSU in Portland, Oregon.
The study for the first time confirms what scientists had suspected: That glial cells aren’t just simple bystanders regulating neurons within the brain, but they also play active roles in processing information in the brain.
The researchers studied astrocytes, star-shaped glial cells that comprise roughly 35 percent of the cells in the human brain. Astrocytes, which closely associate with neurons and in particular synapses, were previously known to perform a supporting role for neurons by providing oxygen, sugars and removing carbon dioxide as needed. However, the new paper for the first time reveals that neurotransmitters released by neurons bind astrocytes, change calcium signaling in astrocytes, and astrocytes in turn regulate downstream neurons. Moreover, such signaling events were essential for behavior, from simple olfactory responses to more sophisticated changes in behavior after a “startle” response.
“We found that astrocytes are not just simple bystanders,” Freeman said. “They actually play a very important role as neuromodulators regulating attention, anxiety and mood, for example.”
Freeman said the next phase of research will seek to determine how widely this type of signaling occurs in the brain. Researchers also will explore the influence of astrocytes on neuromodulators like dopamine or serotonin.
Freeman authored the study while part of the Howard Hughes Medical Institute at the University of Massachusetts Medical School. Co-authors include Zhiguo Ma and Tobias Stork of the Howard Hughes Medical Institute and Dwight E. Bergles of Johns Hopkins University School of Medicine.
The work was supported NINDS grant R01 NS053538.