A team of researchers from the University of Washington has succeeded in inducing a state very similar to hibernation in mice and rats through brain stimulation. The authors have applied ultrasound to the hypothalamus of these animals to produce and maintain a state called torporin which there is a reduction in metabolism and body temperature to save energy.
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The details are offered by Hong Chen’s team in a work published this Thursday in the magazine Nature Metabolism. The authors have applied a non-invasive technique to temporarily activate the specific nerve cells that regulate this state in the brain and believe that if it could be applied in humans it could have clinical applications for cardiovascular accidents or severe trauma.
And, dreaming longer term, it may be a way to induce suspended animation in astronauts on future space travel.
Reducing energy consumption
Lethargy is a physiological state characterized by a reduction in body temperature and metabolic activity that many animal species apply to reduce energy consumption in periods of scarcity of resources or in hostile conditions for survival. This state is controlled by the central nervous system and by a group of specific neurons located in the preoptic area of the hypothalamus.
The result was an immediate drop in body temperature of several degrees (on average 3 to 3.5°C).
Chen’s team developed an ultrasound emitter that could be mounted on the head of mice while they moved freely and aimed 10-second ultrasonic pulses at this region of the brain. The result was an immediate drop in body temperature of several degrees (on average 3 to 3.5°C), reduced heart rate, and reduced oxygen consumption in both male and female mice, from which the animals became They recovered after two hours.
Effects maintained over time
To avoid unnecessary excessive stimulation, the researchers devised a system to prolong torpor over time by minimizing the number of stimuli. This automated system delivered a repeated ultrasonic pulse once body temperatures began to rise, allowing them to keep the animals in this state of torpor for up to 24 hours, without signs of harm or discomfort.
The authors had success with animals without torpor, such as rats, even though their body temperatures only dropped by an average of 1 to 2°C.
Producing torpor in mice was relatively easy considering that it is a species that applies this strategy naturally, but would it work with a species that does not enter torpor like rats? To verify this, the scientists applied the same technique to 12 rats and achieved good results, although their body temperature only dropped by an average of 1 to 2°C.
This result leads the researchers to believe that the physiological processes that regulate the metabolic response could be present in mammals that do not hibernate and could be induced in a non-invasive way, as they have done with mice. Although they acknowledge that more work is needed, they argue that it is worth further investigating its possible future application in humans. This non-invasive and reversible technique to slow metabolism and reduce body temperature could have applications in medicine, potentially after acute emergencies or severe acute illness.
The specialists consulted by elDiario.es They consider the results to be very interesting in general, although it will be necessary to see how they are extrapolated to animals with very different hypothalamuses, such as primates and potentially humans. For Antonio Oliviero, a neuroscientist at the Hospital for Paraplegics in Toledo who works with brain stimulation, this is extremely interesting work that opens up many possibilities.
“We will have to be sure that it works, but if it is confirmed in the future, the applications are endless,” he says. The specialist recalls that one of the most powerful protectors after a trauma is to reduce the temperature and induce hypothermia, which is not easy to apply and is now induced physically, by cooling or administering drugs. “If it worked in animals with very different hypothalamuses, such as primates, clearly this would allow metabolism to be lowered in a reversible, modelable way.”
It would be a much more natural way to apply an induced coma, instead of doing it with a drug
The neuroscientist Javier Cudeiro, a specialist in neuromodulation, believes that this is formally “exquisite” work, although, like Oliviero, he misses that the authors had recorded the brain activity of the mice using an electroencephalogram (EEG), to verify What state are they in during the process? Beyond the fantasies about space travel, the most relevant thing, in his opinion, is its possible application in routine clinical processes, such as very serious trauma. “It would be a much more natural way to apply an induced coma, instead of doing it with a drug.”
“The experiments are well conceived, since tests are carried out both in a hibernating animal (mouse) and in a non-hibernating animal (rat),” agrees Matteo Cerri, Associate Professor of Physiology at the University of Bologna (Italy), in statements to SMC Spain, although he judges that the main limitation is “the very modest effect of the technology on rats” which leads him to think that there is still a lot of work to be done. “I think this technology will be useful in specific conditions where even modest hypothermia can already be very beneficial, rather than for interplanetary travel,” he says.
The study is not a frikada. If it is true that it can be applied to humans, a new era will open
The most relevant question, in addition to whether it works, is whether it causes any kind of damage or dysfunction in the brain, since it involves constant stimulation in such a delicate control area as the hypothalamus. “I would be very interested to know if ultrasound stimulation of the preoptic area of the hypothalamus induces an altered state of arousal and consciousness or maybe even sleep,” Vladyslav Vyazovskiy, Professor of Sleep Physiology at the University of Oxford, tells SMC. “The question remains whether we are inducing a normal physiological hibernation or an abnormal state,” he says. “You have to be careful because it can have very negative consequences for the body and the brain if it is imposed.”
Oliviero manifests himself in the same line. “They would have to see if there are unwanted effects, if the mouse wakes up completely crazy they don’t know it,” he says. In any case, and although there will be sensational headlines about the future of space travel, the work “is not a geek”, but may open the door to a new field of research in the next five or ten years if the developments continue. appropriate steps and it is verified that it works. “If it is true that it can be applied in humans, a new era will open,” he concludes, “the era in which we will be able to reduce metabolism and the state of alertness safely and non-invasively.”