They successfully test the use of ultrasound in the brain to induce a state of hibernation

Space travel poses a challenge to the human body. There are patients whose ailments accelerate the countdown of their vital clock. If there was a way to stop everything and gain time, it would open up a possibility to 'wait' for a new option or to avoid wearing down the body. Now, a group of scientists from the University of Washington have managed to induce a state very similar to hibernation.. A proof of concept that they have managed to successfully overcome in rats and mice.

To do this, they have directed ultrasound towards a specific area of the brain and have managed to induce a state, called torpor, which involves a slowing of metabolism and body temperature to save energy.. According to the authors, who publish the results in the journal Nature Metabolism, if it could be applied in humans it could be used in space travel or in medicine, to increase the chances of survival in life-threatening situations such as heart attacks or strokes..

Reaching that state of torpor, which in Nature is found in species such as hummingbirds and bats on a daily basis or seasonally in the hibernation of bears or the aestivation of worms, is achieved through the alteration of the system central nervous system, which is in control. Ultrasound waves can non-invasively access the skull to target the brain and, if focused on neurons, have been shown to activate nerve cells in animals.

How is hibernation induced in mice?

The team led by Hong Chen and Yaoheng Yang, from the Division of Neurotechnology at the University of Washington, has invented an ultrasound emitter that is placed on the head of freely moving mice.. The mechanism targets 10-second ultrasonic pulses at the preoptic area of the hypothalamus, a region of the brain known to regulate hibernation..

This triggers an immediate drop in body temperature of several degrees (an average of 3 to 3.5°C), along with reduced heart rate and decreased oxygen consumption in both male and female mice.. Two hours later, the animals had fully recovered..

Once this test was passed, they proposed to extend the temporary state of hibernation for 24 hours. To do this, the authors combined their ultrasound emitter with an automated system that delivers a repeated ultrasonic pulse once body temperatures begin to rise, and they were able to keep the animals in this state of torpor for an entire day, without finding any signs of sleep. hurt or discomfort.

In the paper, the authors also show that the technique has worked in 12 rats, an animal that does not hibernate naturally, although its body temperature was only reduced by an average of 1 to 2°C.. With this they suggest that the physiological processes that regulate the metabolic response could be present in non-hibernating mammals..

Work on the mechanism to achieve this state of protective torpor may seem like a small step for this research group, but it promises to be a big step for humanity to exploit hibernation states in medicine and possibly for deep space travel..

With the series of recent publications, the scientific community has taken important steps towards understanding the role of the brain in inducing torpor.. In particular, Yang and Chen's groundbreaking study fuses a variety of technologies to unlock molecular mysteries and pave the way for non-invasive induction of torpor..

So while more research is needed to see if the approach would work safely in humans, Chen's team argue that a non-invasive, reversible technique to slow metabolism and reduce body temperature could have future applications..

A step that fixes previous attempts

Until now, the non-invasive and safe induction of a state of torpor was limited to science fiction in movies and novels.. Despite several decades of research, it has still not been achieved. The original concept proposed that hibernation is regulated by endogenous blood substances and great efforts were devoted to the search for them, the scientists point out in the work.

Later, it was concluded that the state of torpor is controlled from the central nervous system (CNS), so that a direct intracranial injection of molecules directed at the CNS pathways induced a profound hypothermic state that resembled natural torpor.. And it has been a series of recent groundbreaking studies that have identified various groups of neurons in the preoptic area of the hypothalamus that regulate torpor and hibernation in rodents..

Genetic engineering of these neuronal populations for optogenetic and chemogenetic manipulation yielded critical torpor-hibernation physiological and behavioral characteristics in mice.. Although these technological advances in inducing a state of torpor are promising, the approaches required either surgical intervention or genetic engineering, limiting the broad application of these approaches and translation to humans, the scientists say..

Ultrasound was billed as “the only energy option available that can non-invasively enter the skull” and be placed anywhere within the brain with pinpoint precision and without ionizing radiation.. “These features, along with its safety, portability, and low cost, have made ultrasound a promising technology for neuromodulation in small animals, nonhuman primates, and humans, although its mechanism remains elusive,” the authors explain in the article. authors.

This is how torpor works in Nature

Torpor and hibernation are found in birds and in all three subclasses of mammals (monotremes, marsupials, and placentals), supporting the idea that torpor is a plesiomorphic feature (meaning it is more ancestral than high rates). metabolism and body temperatures).

“If we accept torpor as a plesiomorphic characteristic”, the authors of an article in the same publication that accompanies the main one, Martin Jastroch and Frank van Breukelen, consider whether it is possible to revive the torpor program in species that have lost the ability to natural to spontaneously enter torpor. We have known for 25 years that at least one species of primate, the fat-tailed dwarf lemur, can enter torpor and hibernation to overcome food shortages during the tropical dry season.. Therefore, other primates (including humans) may, in principle, possess the genetic makeup to cope with hypometabolic states.”.

However, as Jastroch and van Breukelen argue, “dwarf lemurs are, at best, about 100 times lighter than adult humans (600 g vs. 60 kg body weight), which raises the question of Whether hypometabolic states are possible in larger mammals. In bears, hypometabolism occurs during the winter, with basal metabolic rates decreased by up to 75% with only modest effects on body temperature.. Therefore, prolonged hypometabolic states are possible in mammals even larger than humans.”