Being able to put someone in a state of suspended animation may be a step closer after scientists found the trigger in mammal brains that can induce hibernation.
Researchers from the University of Tsukuba and Harvard Medical School identified the ‘snooze button’ in mice that triggered naturally occurring temporary hibernation.
This natural sleeping state was also triggered in rats, who do not usually hibernate or go into torbor, according to the Japanese scientists.
It may be possible to induce synthetic hibernation in humans if it turns out we have the same set of brain cells as the mice and rats involved in this study.
Being able to put someone into suspended animation could improve recovery rates from surgery or illness, the team say. It could also make interplanetary travel safer.
Researchers from the University of Tsukuba and Harvard Medical School identified the ‘snooze button’ in mice that triggered naturally occurring temporary hibernation and say it could be used on humans in the future
Two studies, unrelated but both published in Nature, made a similar discovery – that a neuron could be used to trigger torpor in mammal brains.
In a US study, scientists identified a population of brain cells that control topor and showed that stimulating these brain cells in mice induces torpor.
They found that while blocking these brain cells prevents torpor, the authors wrote.
The researchers say it may be possible to induce synthetic hibernation in humans if we have the same set of brain cells, which could be useful in reducing tissue damage or preserving organs for transplantation.
The team said artificial induction of a hibernation-like state could eventually have medical applications for humans, although this effect has not been tested in people.
Hibernating animals can lower their body temperature to reduce energy expenditure during times of limited food availability, such as the winter.
Previous research has implicated the central nervous system in the regulation of hibernation, but the precise mechanisms involved have been unclear – until now.
To learn more about what drives hibernation, Takeshi Sakurai and colleagues from the University of Tsukuba setup a study of lab mice who do not hibernate.
Mice exhibit a similar temporary hypometabolic state to hibernation called torpor.
Their experiments led to the identification of a distinct set of neurons in the hypothalamus – an import part of the brain responsible for a range of functions.
They are known as Q neurons and can induce long-lasting (more than 48 hours) reductions in body temperature and metabolism, similar to hibernation.
The authors show that these neurons can be activated synthetically with chemicals or light, and uncover the wider circuit of neurons involved in this effect.
No adverse effects on mouse behaviour or damage to tissues and organs were observed following the induced hibernation-like state.
The researchers say it may be possible to induce synthetic hibernation in humans if we have the same set of brain cells, which could be useful in reducing tissue damage or preserving organs for transplantation
To determine whether the induced state was distinct from torpor, the authors repeated their experiments in rats, which undergo neither torpor nor hibernation.
Once again they found that activation of Q neurons induced a hibernation-like hypometabolic state in the rats, just like it did in the mice.
In an independent study, Michael Greenberg and colleagues from Harvard identify a population of neurons within the hypothalamus that regulate torpor in mice.
They demonstrate that stimulating these neurons can drive a mouse to the torpor state, even when there is no shortage of food.
The role of these neurons is confirmed by blocking their activity, which prevents natural torpor from being initiated.
These findings help researchers to understand the neuronal processes that regulate hibernation-like states.
Sakurai and colleagues suggest that these neuronal circuits may be conserved in a broad range of mammals, even in non-hibernating species, and posit that it might be possible to selectively manipulate Q neurons.
Inducing a state of synthetic hibernation in humans could be possible in future.
The two papers related to this study have been published in the journal Nature and can be found here and here.