An international team of scientists has discovered a new type of brain cell hidden among neurons and their supporting units.
The scientists were astonished to discover that the new cell type had characteristics of both, allowing it to take an active role in neural functions while still providing support to the surrounding neural tissue.
The study revealed that what are known as astrocytes are abundant in the brain and wrap around neural connections like 'glue'. For many years, neuroscientists assumed that these cells were completely passive, existing only to protect neurons.
Subsequently, significant evidence emerged that astrocytes may contribute to the 'firing' of neurons by secreting glutamate, the main neurotransmitter in the brain.
However, laboratory studies indicate that astrocytes are capable of releasing and absorbing glutamate, but its role in a living, healthy brain is still under research.
In this regard, researchers from various institutions in the United Kingdom and Europe found a radical hybrid cell in the brains of mice.
Scientist Andrea Volterra from the University of Lausanne in Switzerland says: “Between neurons and astrocytes, we now have a new type of cell at hand. Its discovery opens enormous research horizons.”
Using single-cell RNA sequencing, the researchers identified nine distinct populations of specialized astrocytes in the hippocampus. Cluster 7 stood out interestingly, as it was located in very separate parts of the hippocampus, while possessing all the molecular machinery needed to mobilize and release glutamate.
The researchers found that these specialized cells release glutamate at tiny hotspots that resemble a synapse, which includes the space where two neurons normally communicate by releasing glutamate.
"They are cells that modulate the activity of neurons, controlling the level of communication and the excitation of neurons," explains neuroscientist Roberta DiCeglia, from UNIL.
When these astrocyte-like cells were disabled, the mice showed memory impairment.