Monkey Experiment Reveals a Brain Switch That Could Be Useful For Space Travel : ScienceAlert

For humans to ever get out among the stars, we’re going to have to solve some big logistical problems.

Not the least of these is the travel time involved. Space is so vast and human technology so limited that the time it takes to travel to another star presents a significant obstacle.

Voyager 1, for example, will take 73,000 years to reach Proxima Centauri, the closest star to the Sun, at its current speed.

Voyager launched more than 40 years ago, and newer spacecraft can be expected to travel faster; even so, travel will still take thousands of years with our current technology.

One possible solution would be generator ships, which would see multiple generations of space travelers live and die before reaching their final destination. Another would be artificial hibernation, if it could be successfully implemented.

This is what scientists from the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences have begun to investigate; not in humans, but in monkeys, chemically inducing a state of hypothermia.

“Here, we show that activation of a subpopulation of preoptic area (POA) neurons by a chemogenetic strategy reliably induces hypothermia in anesthetized and freely moving macaques,” the researchers write in their paper.

“Altogether, our findings demonstrate the central regulation of body temperature in primates and pave the way for future application in clinical practice.”

Hibernation and its slightly less comatose state, torpor, are physiological states that allow animals to withstand adverse conditions such as extreme cold and low oxygen.

Body temperature drops and metabolism slows to a crawl, keeping the body in a stripped-down ‘maintenance mode’ – the bare minimum to stay alive while preventing atrophy.

This can be found in some animals, including warm-blooded mammals, but very few primates. Neuroscientists Wang Hong and Dai Ji from SIAT wanted to see if they could artificially induce a state of hypometabolism, or even lethargy, in primates by chemically manipulating the neurons in the hypothalamus responsible for sleep and thermoregulation processes – the preoptic neurons.

The research was conducted on three young male crab-eating monkeys (Macaca fascicularis). In both anesthetized and non-anesthetized states, the researchers applied drugs designed to activate specific modified receptors in the brain, known as Designer Receptors Exclusively Activated by Designer Drugs, or DREADD.

The scientists then studied the results using functional magnetic resonance imaging, behavioral changes, and physiological and biochemical changes.

An illustration showing the role preoptic neurons play in hypothermia. (SIAT)

“To investigate the brain-wide network resulting from preoptic area (POA) activation, we performed fMRI scans and identified multiple regions involved in thermoregulation and interception,” says Dai.

“This is the first fMRI study to investigate functional brain connections revealed by chemogenetic activation.”

The researchers found that a synthetic drug called Clozapine N-oxide (CNO) reliably induced hypothermia in both anesthetized and awake macaques.

However, in anesthetized monkeys, CNO-induced hypothermia resulted in a decrease in body temperature, preventing external rewarming. The researchers say this demonstrates the critical role POA neurons play in primate thermoregulation.

The researchers recorded behavioral changes in awake monkeys and compared them to those of mice with induced hypothermia. Typically, mice decrease activity and their heart rates decrease in an effort to conserve heat.

In contrast, the monkeys showed an increase in heart rate and activity level and, in addition, began to tremble. This suggests that thermoregulation in primates is more complex than in mice; hibernation in humans (if it can be done at all) will have to take this into account.

“This work provides the first successful demonstration of hypothermia in a primate based on targeted neuronal manipulation,” says Wang.

“With the growing passion for human spaceflight, this hypothermic monkey model is a milestone on the long road to artificial hibernation.”

The research is published in The Innovation.