Two groups of researchers have independently discovered a “brain switch” that makes starving mice enter a hibernation-like state called torpor to save energy. They hope it may be possible to induce similar states in people.
“Suspended animation could transform medicine and open the door to fantastic possibilities such as space travel and life extension,” says Sinisa Hrvatin at Harvard Medical School.
Many birds and mammals, from hummingbirds to lemurs, lower their body temperature and enter a state of suspended animation as a way to survive when times are tough. Some hibernate through winters, others enter a state called torpor for hours or days to save energy.
Mice normally enter torpor only when they run out of food, but Hrvatin’s team genetically engineered mice to let them control the activity of certain neurons by injecting a chemical. The team showed that stimulating specific clusters of neurons in the hypothalamus can induce a torpor-like state even in mice that are well-fed, and that inhibiting these cells prevents mice entering torpor.
In a separate study, Takeshi Sakurai at the University of Tsukuba in Japan identified the same brain switch using a different approach. His team looked for neurons in mice that produce a short protein called QRFP, which previous studies had suggested was linked to torpor, and found that stimulating these neurons induced torpor. They also found that stimulating the equivalent neurons in rats had the same effect, even though rats do not enter torpor normally.
Being able to induce a similar state in people could have many uses in medicine, helping to treat everything from cancer to strokes and injuries, but it is not clear whether this switch also exists in humans. “We don’t know if humans have the same cells, and we don’t know if stimulating them would have the same effect,” Hrvatin says.
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