By MARA BOVSUN, UPI Science News
WASHINGTON, March 9 (UPI) -- California scientists say they have shown that, like humans, much of a bug's life is spent sleeping.
They also demonstrated that the sleep-like state in bugs -- fruit flies in this case -- are remarkably similar to mammals and even humans. They nap when very young, stay awake more in their later years and will get a jolt from caffeine that keeps them buzzing into the wee hours.
While the question of whether insects sleep may not have been keeping too many people awake at night, the work may one day help humans sleep better by revealing the genes and biological mechanisms that control slumber.
Neuroscientist Giulio Tononi says this finding gives researchers an easy-to-use laboratory animal to answer some fundamental questions about human sleep, like why or whether it is needed for good health. Tononi says, "We did not know what the function of sleep might be. There are many theories, but it is a mystery." Sleep researchers have been trying to pin down the purpose of sleep for at least four decades. But after all that time, says Tononi, "We are still groping in the dark." He says, "The truth is, we still don't know what it is doing." Down the road, the work could lead to medications that could help the millions of people who suffer from sleep disorders. Or, says Tononi, drug designers could come up with a pill to do away with the need for sleep altogether, something that will give the biological benefits without eight hours of down time. Tononi led the scientific team from The Neurosciences Institute in San Diego. The experiment is described in Friday's issue of the journal Science. This is the second paper to explore sleep-like states in fruit flies. The first was published earlier this year from a team of researchers at the University of Pennsylvania in the journal Neuron. It's been known for years that fruit flies live by circadian rhythms, which means they are quiet at some times of the day and active at others. But, Tononi says, just watching flies and recording their rest periods wasn't enough to prove that they are actually sleeping. So he put his flies through a battery of tests. Tononi says, "We did everything you can do in a fly to show that it sleeps." He measured their movements by monitoring infrared light and sound waves; he banged on their vials; he gave them caffeine and antihistamines; he measured chemicals in their brains during daylight and darkness. He found that, even though they don't close their eyes and roll into a fetal position, sleep in fruit flies has much in common with bedtime for people. First, fruit flies sleep for about the same number of hours, and like human babies, young flies need extra naps while the elderly spend more of time awake. Flies were more alert to noise and movement, like a scientist banging on the walls, during the wake period. Caffeine kept them up, and antihistamines knocked them out. Flies also behaved like humans when they were deprived of sleep, dozing off about seven times more often during the day than flies who were allowed to rest through the night, says Tononi. Molecular and chemical changes seen in the flies in sleep and wake periods mirrored what goes on in rat brains, he says. He believes it is "very likely" that the same kinds of changes happen in humans as well. Tononi says, "There is something fundamental there." In another part of the research, Tononi also looked at a fly with mutant genes and found differences in their sleep like states, something that could explain why some people sleep deeper or longer than others. Asked if they dream, however, Tononi says, "I'm very skeptical about dreaming." Future work in Tononi's lab will look for genes that influence sleep and explore whether sleep deprivation in the fly impairs learning. Sleep expert Charles Czeisler, a professor of medicine at the Harvard Medical School who was not involved with the research, says that taken together the two papers on sleeping fruit flies presents "the exciting prospect that a sleep-like state could be explored in a species in which the genetics have been so extensively studied."