Introducing the brain: microglia have many functions (Introduction)

by David Turell , Tuesday, December 15, 2020, 15:06 (1437 days ago) @ David Turell

Microglia, which are immune cells that protect the brain also control electrical hyperactivity:

https://medicalxpress.com/news/2020-12-unexpected-role-brain-immune-cells.html

"An important part of the brain's immune system, cells called microglia constantly extend and retract "branches" from their cell body to survey their environment. Think of an octopus, not moving its body, but reaching its tentacles in every direction. That's how microglia operate. In the span of an hour, each cell will have covered the entire three-dimensional space that surrounds it. And then, it will start all over again.

"This continuous and rapid surveillance is a unique feature reserved for microglial cells in the brain. It occurs in your brain all the time, without the presence of disease, and whether you are awake or asleep. Microglia can also rapidly direct their branches toward a site of injury in the brain. The longstanding theory has been that microglia perform this surveillance to sense invasion by an infectious agent or to sense trauma.

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"In a recent study published in the journal Nature Neuroscience, she and her team show that, in fact, surveillance by microglia helps prevent seizure activity (or hyperexcitability) in the brain. These findings could open new therapeutic avenues for several diseases, given that hyperexcitability is a feature of many neurological disorders, including Alzheimer's disease, epilepsy, and autism.

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"The scientists discovered that microglia are not extending their branches at random. Instead, microglia reach out primarily to active neurons, one after another, while paying less attention to non-active neurons. Importantly, they noticed that when microglia touch an active neuron, that neuron's activity does not increase further.

"'Microglia seem to sense which neuron is about to become overly active, and keep it in check by making contact with it, which prevents that neuron's activity from escalating," explains the study's other first author, Mario Merlini,..."In contrast, in our mouse model where microglia movements are frozen, we found that the activity of nearby neurons keeps increasing, a bit like a heater with a broken thermostat. This changed our thinking on how neuronal activity is regulated in the brain. Instead of an on-off switch, microglia are the brain's thermostat, controlling excessive neuronal activity".

"These findings helped the team discover a physiological role for microglial surveillance; microglia are essential for maintaining neuronal activity within a normal range by preventing neurons from becoming overactive, or hyperexcitable."

Comment: It is logical that the brain would have its electrical actions under tight controls; such a highly complex system requires design.