Stellar brain cells can be the key to why and how we sleep

Brain astrocytes, which express the amount of fluorescent calcium captured by two photons under a microscope. Loan Image by Ashley Ingios, a gift from modern biology

A study published in the journal Current biology suggests that stellar brain cells, known as astrocytes, may be just as important for sleep regulation as neurons, the nerve cells in the brain.

Washington State University Elson S. Led by researchers at Floyd Medical College, the study provides a new impetus to finally solve the mystery of why we sleep and how sleep works in the brain. The discovery could also provide a basis for further treatment strategies for sleep disorders, neurological diseases and other conditions associated with restless sleep, such as: PTSD:, depression, Alzheimer’s Disease խանգ Autism Spectrum Disorder.

“Everything we know about sleep is based on neurons,” said Ashley Ingios, lead author of Associate Research in Postdoctoral Research. He explained that neurons communicate through electrical signals that can be easily detected by electroencephalography. Astrocytes, a type of glial (or “glue”) cell that interacts with neurons, do not use electrical signals; instead, they use a process known as a calcium signal to monitor their activity.

It has long been thought that astrocytes, which can outnumber neurons by one in five, simply play a supporting role without direct involvement in behaviors or processes. Only recently have neuroscientists begun to look more closely at their possible role in various processes. And while several studies have suggested that stellar cells may play a role in sleep, there have not been solid scientific tools to study their calcium activity until recently, Ingios said.

The study goes out the window into the brain

To further explore the role of astrocytes in sleep, he and his co-authors used a rodent model to record the calcium activity of astrocytes during sleep, as well as after sleep deprivation. They used a fluorescent calcium sensor, pictured with tiny microscopes on their heads, that looked directly into the mice’s brains as they moved and behaved as usual. This indicator allowed the team to see how calcium-based fluorescent activity is dispersed during sleep-wake behavior in horoscopes. Using their miniature microscopes, their unique methodology allowed the team to study the calcium activity of astronomers in sleep for the first time in free-ranging animals.

The research team set out to answer two main questions. Do astrocytes change dynamically like neurons in the waking state? And do astronomers play a role in regulating the need for sleep to regulate our natural urge to sleep?

Looking at the astrocytes in the cortex of the frontal lobe, the part of the brain associated with measurable EEG changes in sleep need, they found that the activity of astrocytes changed dynamically through the sleep-wake cycle, as it does neurons. They also noted the maximum calcium activity at the beginning of the resting phase when sleep needs are greatest, and the lowest calcium activity at the end of the resting phase when sleep needs are dispelled.

Next, they kept the mice awake for the first 6 hours of their normal resting phase, observing a change in calcium activity in parallel with the slow-wave EEG activity, an important indicator of sleep. That is, they found that lack of sleep caused an increase in the star’s calcium activity, which decreased after the mice were allowed to sleep.

Their next question was whether genetically manipulating the activity of stellar calcium would affect sleep regulation. To find out, they studied mice that lacked the protein known as STIM1 selectively in astrocytes, which reduces the amount of calcium available. After sleep deprivation, these mice did not sleep or fall asleep for as long as normal mice that were allowed to sleep once, which later confirmed earlier findings suggesting that astrocytes may play a role in regulating sleep.

Finally, they tested the hypothesis that the calcium activity of astrocytes may simply reflect the electrical activity of neurons. Studies have shown that the electrical activity of neurons is synchronized during non-REM sleep հետո after sleep deprivation, but researchers have found that the opposite is true for astrocytes.

“This shows us that astrocytes are not only passively pursuing the lead of neurons,” said Ingios. “And since they do not necessarily exhibit the same modes of activity as neurons, this may actually play a more direct role in regulating the need for sleep for theocytes.”

The direction of further research

More research is needed to further understand the role of astrocytes in the regulation of drowsiness, says Ingios. He plans to study the calcium activity of astrocytes in other parts of the brain that have been shown to be helpful for sleep. In addition, he would like to study the interactions of star cells with different neurotransmitters in the brain to begin to break down the mechanism by which star cells can induce sleep.

“The results of our study suggest that we may have been looking for the wrong place for more than 100 years,” said Marcos Frank, senior author and professor of biomedical sciences. “It provides strong evidence that we need to target astrocytes to understand why we sleep, as well as to develop therapies that can help people with sleep disorders and other health conditions that are abnormally sleepy. contains “.

Reference. “The Role of Astronomical Calcium in the Regulation of Mammalian Sleep” by Ashley M. Ingiosi, Christopher R. Hayworth, Daniel O. Harvey, Kristan G. Singletary, Michael J. Rempe, Jonathan P. Wisor, Marcos G. Frank, 2020 . On September 24, Current biology,
DOI: 10.1016 / j.cub.2020.08.052:

The study was supported by the National Institutes of Health.

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