In an unexpected turn of events, researchers at the University of Basel have challenged the traditional understanding of sleep regulation in vertebrates. Contrary to popular belief, not all animals, such as some fish species, require orexin to maintain their sleep-wake rhythm, unlike humans for whom orexin is crucial. Orexin, a molecule essential for controlling normal wake and sleep patterns in vertebrates, is notably absent in certain fish species.
For the past two decades, fish have served as a vital model for investigating sleep behavior and its regulation, assuming that vertebrates share similar mechanisms in this regard. However, a recent study led by Professor Alex Schier has shed new light on this subject. The team’s research on Clown loaches, a South Asian fish species commonly found in zoos and aquariums, revealed that these fish have normal sleep patterns without the presence of the orexin signaling pathway.
Dr. Vassilis Bitsikas, the study’s first author, expressed surprise at the findings, highlighting that clown loaches can easily awaken despite lacking orexin, unlike individuals with narcolepsy who rely on the molecule for regulating their sleep-wake cycle. This discovery challenges the conventional belief that orexin is indispensable for maintaining the sleep-wake rhythm in all vertebrates.
Initially focusing on studying the orexin pathway in clown loaches, the researchers observed the fish’s sleeping behavior, noticing their unique characteristics when at rest. Further investigations exposed the fish’s lack of a functional orexin signaling pathway. Additionally, the team discovered that zebrafish also exhibit normal sleep-wake behavior without relying on orexin, proposing the presence of alternative sleep control mechanisms in these species.
The newfound insights into fish’s sleep regulation mechanisms have not only expanded our comprehension of sleep and wake regulation but also raised intriguing questions about the evolutionary development of distinct control systems in vertebrates. By investigating the reasons behind these variations, researchers hope to uncover valuable insights into why some animals are more susceptible to sleep disorders like narcolepsy.
The utilization of fish as model organisms has been instrumental in exploring the evolution of sleep, and the latest discoveries emphasize the potential of these aquatic species in unraveling the mysteries of sleep regulation. As the research progresses, the intricate mechanisms governing sleep behavior in different species may provide essential clues to understanding the complexities of sleep disorders and pave the way for innovative treatments and interventions in the future.