It has been widely accepted that memory formation is mainly due to neurons, the brain cells responsible for relaying chemical and electrical messages. A new study, however, suggests that these cells have collaborators called pericytes, which may have been unnoticed for so long.

What are Pericytes?

Pericytes refer to multi-functional mural cells that wrap around endothelial cells throughout the body. They are located in the basement membrane, enabling them to communicate efficiently. These cells can form direct connections with adjacent cells by forming gap junctions between them, allowing the exchange of ions between both cells. Pericytes use integrins to communicate with endothelial cells that are not adjacent to them.

Formerly called Rouget cells, pericytes are found in the walls of tiny blood vessels called capillaries, which play a crucial role in regulating blood flow in the brain. They also perform other functions, such as forming blood vessels, controlling the entry of immune cells into the central nervous system, and maintaining the blood-brain barrier.

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Cellular Mechanisms for Memory Formation

Aside from these jobs, pericytes also work with neurons in forming and storing long-term memories. This was revealed by the study conducted by Kiran Pandey and colleagues on laboratory mice.

In this study, the experts focused on insulin-like growth factor 2 (IGF2) protein. This hormone is produced in surges in the hippocampus, a crucial region of the brain for making long-term memories. For instance, an uptick in IGF2 can be observed in an animal after being trained to be fearful of scenarios that they can associate with a mild electric shock to the foot.

The pericytes in mice and rats produced most of this IGF2 in the hippocampus. This production seemed to be triggered by the mechanisms of nearby neurons. When memories start to form, neurons in the hippocampus send a flurry of chemical messages to each other. Meanwhile, the communication channels between those cells start to grow stronger. Although the researchers are still unsure how this action activates the surrounding pericytes, they believe that the neurons kick off the process of making memories.

In other experiments, Pandey and her team stopped pericytes from making IGF2 but did not stop different types of cells from doing so. This hindered rodents' ability to make long-term memories and blocked the action of the genes that normally switch on in neurons during memory production.

Taken together, the results of the experiments reveal that pericytes need to produce IGF2 for neurons to make long-term memories successfully. According to senior study author Cristina Alberini, the study allows them to understand the cellular mechanisms that enable memories to be formed and stored. She further described its significance as understanding the cooperation among various cell types can help them advance therapeutics to address memory-related problems. The findings can also have implications for research about brain memory as its associated disorders such as Alzheimer's disease.

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