Scientists from Ohio State University's Institute of Behavioral Medicine Research have discovered that a model of social stress can increase inflammation among brain cells, providing new insight into how the stress response in the brain affects inflammatory and behavioral responses.
The findings may also provide new targets for drugs treatments in the continuing struggle to curtail depression and anxiety.
John Sheridan, professor of oral biology, and Jonathan Godbout, an assistant professor of molecular virology, immunology and medical genetics, turned to colonies of mice to make their discoveries.
Groups of mice living together quickly adopt a hierarchy ranging from dominant to subordinate. This vaguely political system controls the interaction among the animals.
Once these patterns had been established, the researchers then added an additional, highly aggressive mouse to the mix for a two-hour period each day to disrupt the social hierarchy.
With no place to retreat, the mice were forced into conflicts with the new aggressor. After as few as three episodes with the aggressor, the original mice showed distinct signs of what the researchers considered "anxiety-like behaviors."
"These animals can't flee, so they have to stand and fight," Sheridan explained.
The real discoveries came when the researchers analyzed what was happening in the animals' brains and in their immune response.
"We found that in the stressed animals, a certain type of immune cell (myeloid progenitor cell, or MPC), produced in the bone marrow, entered the circulatory system and migrated to the brain," explained Godbout.hese MPCs might normally relocate in this way to deal with an infection or an injury in the brain, but in this case, they moved solely because of the response to a social stressor, he said.
The findings are evidence of a two-way communication that exists between the body and the brain in times of stress, Sheridan said.
The study has been detailed in the latest issue of the Journal of Neuroscience.