AsianScientist (Mar. 2, 2022) – Astrocytes, which are brain cells known chiefly for the upkeep of neurons, could be involved in more complex mental tasks such as reading or tasting food, suggests a new study in mice by researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) in Japan. The findings, which were published in Science Advances, may help researchers understand various neurological disorders in the future.
For long, neuroscientists thought that the astrocytes were the central nervous system’s housekeepers, involved in menial jobs such as delivering food to neurons — the workhorses that manage all the cognitive load. But studies over the last three decades have changed that notion. Scientists now know that astrocytes work alongside neurons to help the brain manage a host of everyday tasks such as walking, using senses or even forming memories.
The latest findings go “one step further towards this direction” of thinking, Bernd Kuhn, professor and head of the optical neuroimaging unit at the OIST, told Asian Scientist Magazine. Kuhn is one of the co-authors of the study.
For the study, the researchers used a combination of sophisticated tools, including a two-photon microscope, to zoom in on the brains of mice as they ran on a cylindrical treadmill and took a breather in between.
In particular, the researchers observed the levels of calcium ions, which are essential to keep a cell running in good condition, inside an astrocyte. When a cell is buzzing with activity, the concentration of these ions shoots up. The team’s analysis showed that the jump in calcium ion levels in astrocytes lasted only 200 milliseconds in some cases. Such speedy fluctuations in calcium ion activity are known to occur only in neurons. “It sort of makes astrocytes much more interesting because they might be really involved in information processing,” says Kuhn. In other words, the astrocytes could be active players in daily activities such as reading, tasting food, or coordinating movement.
Using time-lapse videos of calcium ion changes over a period, say 20 minutes, the researchers were able to identify maps of calcium ion activity that reflected particular behaviors. “Interestingly, this map changes if the behavior of the mouse is changing,” said Kuhn. So, the running map will look different from the one corresponding to the mouse’s resting phase.
These maps could mean, Kuhn said, that astrocytes contribute to storing certain types of memories. Generally, networks of neurons in the brain are responsible for specific things we do, such as moving a limb or turning the head and over time these movements get stored as memory in the networks. The researchers now think that the astrocytes might also be involved in that process.
Kuhn’s group also fine-tuned the two-photon microscope and other tools to unravel the inner workings of single astrocytes, paving the way for neuroscientists to study these cells with more precision.
These findings may allow scientists to study diseases that involve the malfunction of astrocytes in the future. “If we can look carefully at these maps and access activity patterns, this [will allow] us to recognize earlier any abnormalities in these cells,” said Kuhn.
The next step for Kuhn’s team is to elucidate the mechanisms behind the complex dance between astrocytes and neurons — something that scientists still don’t fully understand.
The article can be found at: Georgiou et al. (2022) Ca+ activity maps of astrocytes tagged by axoastrocytic AAV transfer
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Source: Okinawa Institute of Science and Technology Graduate University; Photo: Shutterstock.
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