In a new study, researchers reduced the core body temperature of crab-eating macaques purely by controlling their brains. The study aims to find a way to induce hibernation in monkeys and, eventually, in humans.
Hibernation enables mammals such as bears and rodents to survive adverse weather conditions or a lack of food. During this deep sleep state, they enter a kind of energy-saving mode. Breathing, heart rate, and energy consumption are all drastically reduced; their body temperature plummets, and their metabolism and the chemical reactions that keep them alive slow. Scientists call this condition' torpor.' Animals hibernate by alternating between long periods of torpor and brief periods of arousal, during which they wake up to feed.
Recreating hibernation in humans
So far, understanding and recreating animal torpor has proven difficult. However, researchers from the Shenzhen Institute of Advanced Technology (SIAT) in China have found a way to chemically trigger a state of hypothermia in monkeys. This resulted in reduced body temperature and lower energy requirements.
The team targeted a part of the hypothalamus known as the preoptic area (POA), which is considered to control thermoregulation. They did this by using a synthetic drug and a brain scan.
Illustration of how preoptic neurons drive hypothermia(SIAT)
"To investigate the brain-wide network as a consequence of preoptic area (POA) activation, we performed fMRI scans and identified multiple regions involved in thermoregulation and interoception. This is the first fMRI study to investigate the brain-wide functional connections revealed by chemogenetic activation," said Dai ji says, neuroscientist and author of the study.
The team first infected the POA's neurons with viruses that cause receptors to respond. When researchers administrated the synthetic drug Clozapine N-oxide, they found that it reliably triggered hypothermia (lower body temperature) in anesthetized and awake monkeys.
In the anesthetized experiments, surprisingly, CNO-induced neuronal activity induced a decrease in core body temperature, preventing external heating. According to researchers, this demonstrates the critical role POA neurons play in primate thermoregulation.
The researchers also looked at how the monkeys' bodies and behaviors changed when their body temperature was lowered. Similar experiments on mice and rats resulted in decreased activity and lower heart rates in an attempt to conserve heat. By contrast, the monkeys kept moving around, their hearts were beating much faster, and they were shivering – all in an effort to combat the falling body temperature.
Will interstellar travel ever be possible?
Space travel has long been concerned with the question of how astronauts will be able to travel longer and farther in the future. Hibernation could be the solution.
However, the current study shows that the primates' thermoregulation mechanism is much more complex than in mice. Any hibernation trials in humans (if it can be done at all) will need to take this into account.
"This work provides the first successful demonstration of hypothermia in a primate based on targeted neuronal manipulation," said Dr. Wang Hong from SIAT and the study's author.
"With the growing passion for human spaceflight, this hypothermic monkey model is a milestone on the long path toward artificial hibernation," said Dr. Wang Hong
The research has been published in The Innovation.
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