The Lasker Award, often called a stepping stone to the Nobel Prize, has gone to a University of Tsukuba professor for discovering orexin, a substance in the brain that plays a major role in sleep and wakefulness. The American medical prize recognized Yanagisawa's work, and the researcher who actually purified orexin was Takeshi Sakurai, now vice director of the university's International Institute for Integrative Sleep Medicine, who was in the same laboratory at the time.
Sakurai, who now works at one of the world's leading sleep research institutions, has made induced hibernation his main pursuit: deliberately putting humans into a hibernation-like state. He discussed the prospects on ABEMA Prime, along with more basic questions about how sleep and hibernation differ.
A mouse that stopped moving
Sakurai said the hibernation work grew out of an accidental observation. While studying the function of nerve cells that produce a brain substance he had found, a graduate student running an experiment to activate a specific set of neurons saw a mouse stop moving entirely, as if dead, and turn very cold.
“When we looked into it, we found it was a state that would not be unreasonable to call hibernation, and that is where my interest started.”Takeshi Sakurai, vice director, International Institute for Integrative Sleep Medicine, University of Tsukuba
The experiments now use mice, which do not normally hibernate. Stimulating a specific part of the brain with a laser makes the animals release heat from their tails and begin to cool. Body temperature falls by close to 10 degrees Celsius in about 90 minutes, and heart rate, breathing and metabolism as a whole drop, producing a state similar to hibernation.
Repeating the state many times caused no health problems and no side effects were confirmed, according to the account given on the program. Sakurai's team has also begun work with monkeys, using a virus to make them express an artificial receptor so that "Q neurons" can be stimulated.
Hibernation is not sleep
Asked about the difference between the two, Sakurai said they are entirely different: sleep is sleep, hibernation is hibernation. Sleep is not rest, he said. The brain is busy adjusting synapses, the connections between nerve cells, and fixing memories. In hibernation those functions are heavily suppressed.
Consciousness during hibernation is almost absent, he said. When electrodes are inserted into the cerebral cortex, it is barely functioning.
Hiroyuki Nishimura, the founder of 2channel, asked whether long-term hibernation might work through repeated cycles: the body still needs energy, the parts that must never stop keep running, and the animal wakes when something runs short before being put under again. Sakurai said it is not well understood why mid-hibernation waking is necessary. One theory, he said, is that because hibernation and sleep are different, an animal cannot sleep while hibernating and so wakes occasionally to sleep.
Akira Takei, a former official at the Ministry of Economy, Trade and Industry, asked whether people could become short sleepers who recover in about five hours what normally takes eight. Sakurai said a true short sleeper is not a technique and cannot be trained into the brain. The genuine short sleepers, thought to be about one in several thousand people, are that way by heredity and constitution, he said.