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Ultrasound can set off a hibernation-like state in mice and rats



A standard dormouse in a state of torpor

Simon Phillpotts/Alamy

Zapping a part of the mind with centered ultrasound can put mice in a hibernation-like state referred to as torpor for not less than 24 hours. The identical strategy also can induce the state in rats, which, in contrast to mice, don’t naturally enter torpor.

“That has huge implications,” says Hong Chen at Washington College in St. Louis. “The thinking is that, if we show that in animals that don’t normally enter the torpor state we can still induce a similar phenomenon, maybe we can scale up the technology to larger animals.”

If this may be finished in folks, too, it might have medical makes use of amongst different issues. For example, inducing torpor in individuals who have had strokes might purchase them time and assist restrict the injury, says Chen.

Many warm-blooded animals decrease their physique temperature and decelerate their metabolism to avoid wasting power, getting into torpor. Some bats and birds go into torpor at evening. Others, similar to mice, enter it solely when meals runs low. Hibernation entails prolonged durations of torpor interrupted by occasional returns to regular physique temperature.

In 2020, two groups independently found that stimulating a part of the hypothalamus within the brains of mice can induce torpor. Nevertheless, they used advanced strategies, together with genetic engineering, to activate this “brain switch”.

Chen questioned if ultrasound may very well be used as an alternative. Her staff has been growing a technique referred to as centered ultrasound for treating mind illnesses.

Chen’s staff discovered {that a} 10-second pulse of ultrasound centered on the mind swap space in mice led to their physique temperature falling by round 3°C (5.4°F). The mice recovered fully after 2 hours, however by delivering repeated pulses every time their physique temperature began to rise, it was attainable to maintain the animals on this state for twenty-four hours with no signal of unwell results.

It is likely to be attainable to keep up this state for for much longer, says Chen, however her staff hasn’t but tried to do that.

Whereas the approach additionally works in rats, their physique temperature solely fell by round 1.3°C (2.3°F).

“Although modest, this is important because rats are non-hibernators and, in this, closer to humans,” says Matteo Cerri on the College of Bologna in Italy, whose staff has induced torpor in rats and pigs by chemically inhibiting part of the brainstem.

Reducing physique temperature with ultrasound may very well be helpful for medical functions, however interplanetary journey might require extra strong methods to suppress metabolism, says Cerri.

Precisely how the centered ultrasound induces torpor isn’t clear, says Takeshi Sakurai on the College of Tsukuba in Japan, whose staff was one of many two that found the hypothalamus swap.

It is likely to be triggering this mind swap, says Sakurai. “However, there are also other groups of neurons in the nearby region that play a role in thermoregulation, making it more likely that they are also involved.”

Chen thinks {that a} mixture of the native heating and bodily motion induced by the centered ultrasound opens ion channels on neurons, activating them. However this stays to be established.

Any potential human makes use of are nonetheless far off, she says. “Safety is a big concern.” Centered ultrasound that’s too intense or that’s maintained for too lengthy can injury the mind, and her staff needed to do a number of experiments to work out a secure dose in a mouse.

However it’s fully possible to develop a helmet that might ship centered ultrasound pulses to the equal a part of the human mind, she says.


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