• Wed. Jun 7th, 2023

Ultrasound brain pulses place mice in a hibernation-like state | Science


May 26, 2023

It is a classic science fiction trope: Astronauts on an interstellar journey are kept in sleek, refrigerated pods in a state of suspended animation. Though such pods stay purely fictional, scientists have pursued analysis into inducing a hibernation-like state in humans to lessen the harm triggered by health-related situations such as heart attacks and stroke, and to cut down the tension and expenses of future extended-distance space sojourns.

In a study published these days in Nature Metabolism, scientists report that they can trigger a comparable state in mice by targeting portion of their brain with pulses of ultrasound. Some specialists are calling it a main technical step toward attaining this feat in humans, whereas other individuals say it is a stretch to extrapolate the benefits to our species.  

“It is an remarkable paper,” says Frank van Breukelen, a biologist who research hibernation at the University of Nevada, Las Vegas and co-authored an editorial accompanying the study. The perform builds on a flurry of current research that pinpoint distinct populations of neurons in a area known as the preoptic location (POA) of the hypothalamus. These cells act like an on-off switch for “torpor”—a sluggish, power-saving state the animals enter when they’re dangerously cold or malnourished. In prior research, scientists genetically engineered these neurons to respond to light or particular chemical substances, and identified they could result in mice to enter a torpid state even when they have been warm and effectively-fed. Such invasive tactics can not be simply translated to folks, having said that, Breukelen notes. “That’s truly not going to take place in folks.”

The new ultrasound study, led by bioengineer Hong Chen and her group at Washington University in St. Louis needed no genetic engineering. Chen knew from prior analysis that some neurons have specialized pores known as TRPM2 ion channels that modify shape in response to ultrasonic waves, such as the subset of POA cells that controls mouse torpor. To see what impact that had on the animals’ behavior, her group subsequent glued miniature, speakerlike devices on the heads of mice to concentrate these waves on the POA.

In response to a series of three.two-megahertz pulses, the rodents’ core physique temperatures dropped by about 3°C. The mice cooled off by shifting physique heat into their tails—a classic sign of torpor, Bruekelen notes—and their heart prices and metabolisms slowed. By automatically delivering more pulses of ultrasound when the animals’ physique temperatures started to climb back up, the researchers could preserve the mice in this torpid state for up to 24 hours. When they silenced the minispeakers, the mice returned to typical, apparently with no ill consequences.

Chen’s group then repeated the experiment in 12 rats—which do not naturally go into torpor in response to cold or meals scarcity—and identified a comparable impact, though their physique temperatures only dropped by 1°C to 2°C. The researchers say this suggests the approach could perform even in animals that do not ordinarily hibernate.

Breukelen says his self-assurance in the team’s benefits is strengthened by the reality that when the researchers directed the ultrasound to other brain regions, the mice didn’t seem to enter a torpid state. That suggests the animals’ decreased metabolism was certainly triggered by stimulating especially the neurons in the POA, and not just by “scrambling” brain functioning. “I do not assume any person desires a therapy that relies on just turning off the brain, and consequences be damned,” he says. He’s also encouraged that the researchers re-developed the very same impact in rats. Though humans do not naturally hibernate, the potential is identified in species from almost each and every mammalian lineage, from Madagascar’s fat-tailed dwarf lemur to the arctic ground squirrel. Maybe humans, like the rats, also possess a hidden capacity for getting into a thing akin to hibernation, he says.

Other individuals are not convinced. Shaun Morrison at Oregon Well being &amp Science University doubts the scientists truly observed torpor in the mice. Ultrasound stimulation warms up the brain, he says, so it is attainable the researchers have been in reality activating temperature-sensitive neurons in that area, causing the animals to decrease their physique temperatures in response. Even if the impact is genuine, he’s skeptical that we’ll be making use of ultrasound to place astronauts into suspended animation anytime quickly. People’s brains are a great deal larger than the brains of mice and the POA is buried deeper, Morrison notes, producing it a great deal additional challenging to target with the minispeakers Chen and her colleagues employed. “This ultrasound approach is extremely unlikely to perform in humans in the way it does in mice.”

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