Sleep is one of the rare bodily functions that’s as mysterious as it is essential: Scientists are still trying to figure out why and how humans and other animals rest up. But now, scientists at Caltech have discovered three neuropeptides that help worms fall asleep—and they say the discovery could help them understand sleep and insomnia in other animals.
In a recent study in Current Biology, scientists successfully induced insomnia in the tiny roundworm Caenorhabditis elegans (C. elegans) by removing the neuropeptides nlp-8, flp-24, and flp-13. (Neuropeptides are small molecules involved in neuronal communication.) They found that each peptide controlled a different sleep behavior—nlp-8 inhibited defecation, flp-13 suppressed feeding, and flp-24 stopped the worms from moving around—and by blocking those peptides, they could make it impossible for the worms to fall asleep.
“The different neuropeptides may act in parallel to control the sleep state,” researcher Ravi Nath explains. “You can think of the peptides as workers building a house—or the state of sleep. One is like an electrician and the other a plumber, for example, working together as a team.”
In a 2007 study, researchers discovered that sleep in C. elegans is controlled by a single cell: the ALA neuron. By removing the ALA neuron, they were able to stop the tiny worms from sleeping. This time, however, researchers realized they didn’t need to remove the entire neuron to block sleep. They found that removing nlp-8, flp-24, and flp-13, which are found in high quantities inside the ALA neuron, did the trick.
Of course, inducing insomnia in worms is a far cry from understanding insomnia in humans. But scientists hope their research will serve as a stepping stone toward a more sophisticated understanding of the role different neuropeptides may play in a range of sleep functions.
"The idea that multiple peptides work together to control sleep and its individual behaviors may translate to other animals," researcher Paul Sternberg explains. “C. elegans is a simple animal model that allows us to isolate key molecular pathways. We start there and the information trickles up to other animal models."
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