Introducing the brain: more astrocyte studies (Introduction)

by David Turell , Thursday, May 29, 2025, 00:08 (6 days ago) @ David Turell

They ae getting more attention now:

https://www.sciencenews.org/article/silent-cells-surprising-brains

"These findings — from the brains of fruit flies, zebrafish and mice — open new possibilities for therapies aimed at mental illnesses such as depression and schizophrenia. They could also lead to a deeper understanding of how current therapies work.

"Astrocytes used to be thought of as helpers, assisting with grunt work in the brain. These starburst-shaped cells clean up waste between nerve cells, serve as barriers that keeps harmful threats out of the brain and guide nerve cells into forming connections with each other.

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"Astrocytes grow until they meet another astrocyte, and form thousands of connections with other cells, “which means that every square millimeter of the brain is within the domain of an astrocyte,” Guttenplan says.

"Recent discoveries have revealed that the roles of astrocytes include a more sophisticated job: influencing messages at synapses, the connections between two nerve cells or neurons, and influencing behaviors. But how astrocytes were contributing to these neural conversations wasn’t clear.

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"The new results, along with a growing body of research, suggest that astrocytes sense key chemical messages that were commonly thought to be intended for neurons and, in response, change the activity of neurons around them. Astrocytes seem to act as necessary intermediaries that sense key messages and relay them to nerve cells as needed.

"In the spinal cord equivalent of a fruit fly, for instance, a chemical signal called tyramine dramatically changes astrocytes. Tyramine is a “pay attention” signal, enabling astrocytes to respond to other chemical messages, including dopamine, the researchers found. Without the tyramine signal, astrocytes don’t respond to dopamine and other messages.

"The existence of this switch was “stunning,” says study coauthor Marc Freeman, also of Oregon Health and Science University. “The fact that an arousal cue could take an astrocyte from ignoring all of those major neurotransmitters to suddenly listening to everything … it boggles the mind when you think about the implications.”

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“'There’s specificity to [astrocytes] being able to turn on and off the different knobs,” Guttenplan says. “It has effects on [neural] circuits as well as on whole animal behavior.”

"Similar findings came from a study on larval zebrafish, which found that astrocytes could change brain cell activity and control the animals’ behavior. And even more evidence comes from mouse brain cells, where astrocytes sensed norepinephrine, the mammalian counterpart of tyramine, and then altered nerve cell behavior.

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"Understanding why brains evolved to include this layer of astrocyte oversight is a big question, Eroglu says. “There is something really beautiful here that remains to be understood.” She points to a warning issued from her former advisor, the late Ben Barres, a glial cell pioneer at Stanford University: Ignoring the astrocyte is always a mistake. b]"
(my bold)

Comment: The final point of the article tells us do not ignore any facet of an organism. From a design standpoint everyting we see is there for a reason.