In order for humans to ever venture out into the stars, we must solve some daunting logistical problems.
Last but not least, the associated travel time. Space is so vast and human technology so limited that travel time to another star is a significant obstacle.
The Voyager 1 probe, for example, would last 73,000 years to reach Proxima Centauri, the star closest to the Sun, at its current speed.
Voyager was launched more than 40 years ago, and newer spacecraft are expected to travel faster; Even so, with our current technology, the journey would take thousands of years.
A possible solution would be generation ships, where multiple generations of space travelers live and die before reaching the final destination. Another would be artificial hibernation if it could be implemented successfully.
That’s what scientists at the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences have started to investigate; not in humans, but in monkeys by 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.” write the researchers in their paper.
“Taken together, our results 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 lack of oxygen.
Body temperature drops and metabolism slows to a crawl, leaving the body in a meager “maintenance mode” – the bare minimum to stay alive during this time prevent atrophy.
This is found in several animals, including warm-blooded mammals, but very few primates. SIAT neuroscientists Wang Hong and Dai Ji wanted to see if they could artificially induce a state of hypometabolism, or even hibernation, in primates by chemically manipulating neurons in the hypothalamus responsible for sleep and thermoregulatory processes — the preoptic neurons.
The research was conducted on three young male crab-eating monkeys (Macaca fascicularis). In both the 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 DREADDs.
The scientists then examined the results with functional magnetic resonance imagingBehavioral changes and physiological and biochemical changes.
“To examine the brain-wide network as a consequence of preoptical area (POA) activation, we performed fMRI scans and identified several regions involved in thermoregulation and interoception”, Says Dai.
“This is the first fMRI study examining the brain-wide functional connections revealed by chemogenetic activation.”
The researchers found that a synthetic drug called clozapine-N-oxide (CNO) reliably induced hypothermia in both the anesthetized and awake states in the macaques.
However, in anesthetized monkeys, CNO-induced hypothermia resulted in a drop in core body temperature, preventing external heating. The researchers say this demonstrates the critical role POA neurons play in primate thermoregulation.
The researchers recorded behavioral changes in the awake monkeys and compared them to those in mice with induced hypothermia. Typically, mice decrease activity and their heart rate drops to conserve heat.
The monkeys, on the other hand, showed an increased heart rate and activity and also began to tremble. This suggests that thermoregulation is more complex in primates than in mice; hibernation in humans (if it’s even possible) must 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 supercooled monkey model is a milestone on the long road to artificial hibernation.”
The research was published in The innovation.
