![]() ![]() Even mice do not naturally hibernate for days at a time, as they did in these experiments. The researchers conducted a similar experiment in rats, which do not naturally enter torpor, and saw the same effect. More simply, these properties describe torpor or hibernation. The team called these particular cells Q neurons and named the state the animals were in Q-neuron-induced hypothermia and hypometabolism (QIH). And afterward, the rodents revived spontaneously-and unharmed, just as with hibernation. ![]() And selectively activating neurons in specific parts of the hypothalamus sent the animals into a hibernationlike condition that lasted more than two days.ĭuring this period, the mice’s metabolism remained properly regulated. They found that activating QRFP neurons indiscriminately produced a state that lasted for hours. Knowing this, the researchers used a technique known as chemogenetics-in which neurons are genetically modified so that they can be activated using a drug-to look for neurons in the hypothalamus responsible for the effect. The QRFP peptide is found in many parts of the body, but it is especially prevalent in the hypothalamus, a brain region important for thermoregulation. But the gene appeared to serve as a landmark that could steer researchers to relevant metabolism-lowering neurons. In fact, the lowered body temperature and other measures did not disappear when the gene for the peptide was deleted. QRFP itself was not involved in altering the mice’s metabolic rate. The animals’ metabolic rate (measured by oxygen consumption), body temperature, heart rate and respiration all dropped. “The mice stayed still and were very cold: the opposite to what they expected,” says Genshiro Sunagawa, of the RIKEN Center for Biosystems Dynamics Research in Japan, who co-led the study. But when the researchers switched on neurons that were making the peptide in mice, they got a surprise. The team showed that injecting it into animals actually increased their activity. It began with a paradoxical finding about a peptide called QRFP. One of the two studies was conducted by neuroscientist Takeshi Sakurai of the University of Tsukuba in Japan and his colleagues. And more speculatively, such methods might one day approximate the musings about suspended animation that turn up in the movies. It could also ultimately help find methods for inducing hypothermic states in humans that will prove useful in medical settings. ![]() The work paves the way toward understanding how these conditions are initiated and controlled. Two independent studies published in Nature on Thursday identify neurons that induce such states in mice when they are stimulated. The mechanisms that control torpor and other hypothermic states-in which body temperatures drop below 37 degrees Celsius-are largely unknown. Mice enter a state known as daily torpor, lasting only hours, to conserve energy when food is scarce. When bears, bats or other animals hibernate, they experience multiple bouts of a low-metabolism state called torpor for days at a time, punctuated by occasional periods of higher arousal. For some animals, natural states of lowered body temperature are commonplace. But saline transfusions or other exotic measures are not ideal for ratcheting down a body’s metabolism because they risk damaging tissue.Ĭoaxing an animal into low-power mode on its own is a better solution. Closer to reality are actual efforts to slow biological processes to a fraction of their normal rate by replacing blood with ice-cold saline to prevent cell death in severe trauma. ![]() A well-worn science-fiction trope imagines space travelers going into suspended animation as they head into deep space. ![]()
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