Researchers from Linköping University in Sweden have found that microglia, the brain’s immune cells, play a key role in generating feelings of unease and depression during periods of inflammation, such as from a common cold or the flu.
Earlier research has found that microglial cells are activated in neurological diseases such as Alzheimer’s and Parkinson’s and that people affected by these conditions often fall into a negative mood. Meanwhile, other research has proposed that inflammatory processes may play a role in depression. As such, the researchers from Linköping decided to see whether microglial cells play a role in mood regulation during inflammation.
To do so, the researchers used a technique known as chemogenetics to activate the microglial cells in mice when kept in different surroundings. In doing so, they found that mice would subsequently avoid this type of surrounding, signaling to the researchers that they did not like the experience. They also became less tempted by a sweet solution, which they usually find very interesting.
To verify the role of microglial cells in this process, the researchers then sought to see what happened once they were deactivated. When deactivated, they found that even when mice had inflammation, they did not display negative behaviors. As such, the researchers concluded that microglial cells are likely necessary for the feelings of ‘not feeling well’ and withdrawal that many face when battling a cold or flu.
“Our results show that the activation of microglial cells is sufficient to create aversion and negative mood in mice. It’s natural to suggest that similar processes take place in several human diseases. It’s not unlikely that activated microglia contribute to the discomfort and depressed mood in people with inflammatory and neurological diseases”, says David Engblom, lead author of the study.