Ultrasound Pulses to Brain Send Mice Into a Hibernation-Like State

For many animals, life is a cycle of both abundance and scarcity. Hibernating creatures curl up underground during the winter to slow down their metabolism, allowing them to enter spring without food. Even laboratory mice can enter a state called asthenia, a kind of standby mode that conserves energy, if not fed.

It’s something humans have fantasized about themselves for a long time, and if we ever leave this planet and travel into space, we’ll experience our own era of deprivation. . Science fiction writers tend to imagine mystical technology that can keep humans quiescent and survive centuries of silence before spawning new life. For now, it’s an out-of-reach technology.

But as scientists strive to understand states such as lethargy and hibernation, fascinating details about how the brain controls metabolism are emerging. Researchers reported: Journal Nature Metabolism They announced Thursday that they were able to put mice into a lethargic state by targeting short bursts of ultrasound to specific parts of the brain. While it’s unclear exactly why ultrasound produces these effects, the findings suggest that studying the neural circuits involved in insomnia may reveal ways to manipulate metabolism outside the lab. suggests that there is

Ultrasound machines, which generate high-frequency sound waves, are best known for their imaging capabilities. But neuroscientists also use it to stimulate neurons. Properly tuned sound waves can travel deep into the brain, said Hong Cheng, a professor of biomechanics at the University of Washington in St. Louis and author of the new paper. In 2014, William Tyler, now at the University of Alabama at Birmingham, and his colleagues shone ultrasound into sensory areas of the brain and discovered: Enhanced the subject’s sense of touch. The ever-increasing amount of work Investigating ultrasound as a therapeutic method For illnesses such as depression and anxiety.

Interested in the brain regions that regulate body temperature in rodents, Dr. Cheng and colleagues created a tiny ultrasonic mouse cap. The device trained six bursts of 10-second ultrasound on selected regions of the rodent brain (researchers studying the brain with equipment must be carefully adjusted to avoid possible heat build-up).

Researchers noticed that the mouse had become immobile. Measurements of their body temperature, heart rate, and metabolism showed marked decreases. After ultrasonic bursting, the mice remained in this state for approximately 1 hour and then returned to normal.

By looking closely at the neurons involved in this response, the researchers identified a brain membrane protein, TRPM2, that appears to be sensitive to ultrasound. When the researchers lowered the protein levels in mice, the mice became more tolerant to the effects of ultrasound.

This is an important step toward understanding how ultrasound affects neurons, said researchers at the Icahn School of Medicine in Mount Sinai, New York City, who use ultrasound to study the brain. said Davide Folloni. Little is known about the details.

However, it is possible that not only the ultrasound itself, but also the heat generated by the ultrasound affects TRPM2 in the mouse brain. Raised in an interview. They studied neurons in this brain region and their relationship to numbness. Both may be involved, Dr. Chen said.

In one of the most intriguing parts of the study, the researchers wanted to see if animals that don’t normally experience helplessness (rats) behaved differently when brain regions were stimulated with ultrasound. It is what I did. Indeed, their movements slowed down and their body temperature seemed to drop.

“Rat data are tricky,” warns Dr. Chen. So far they only have information about temperature, not about metabolic rate or other factors.

Could ultrasound be a way to alter the metabolism of large animals like humans who have no history of insomnia? That’s an interesting idea, says Dr. Sakurai.

“At this stage, it remains an open question,” he said.

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