Fish reveal new depths in sleep regulation

In a study that challenges long-held beliefs about sleep regulation across vertebrates, researchers at the University of Basel have made a surprising discovery. The experts found that certain fish species, including clown loaches found commonly in zoos and aquariums, do not require the orexin molecule to regulate their sleep-wake cycles.

Researchers previously deemed this molecule essential for normal sleep and wakefulness in vertebrates. In humans, the absence of orexin has been linked to narcolepsy – a condition that features excessive daytime sleepiness, sudden loss of muscle tone, and uncontrollable sleep attacks.

Model organisms for sleep regulation

For over two decades, fish have been key in sleep regulation research, based on the belief that all vertebrates share similar sleep control mechanisms.

Yet, Professor Alex Schier’s team at the University of Basel’s Biozentrum made a significant discovery. They found that clown loaches and zebrafish defy the common belief by maintaining normal sleep without the orexin pathway.

Study first author Dr. Vassilis Bitsikas found this surprising. He noted that despite lacking orexin, clown loaches do not exhibit narcoleptic symptoms. This hints at unique sleep mechanisms in these fish.

Initially, the researchers focused on orexin in clown loaches, noted for their distinct sleep behavior. Their lack of the orexin pathway sparked further exploration into their unique sleep regulation methods.

The evolution of sleep regulation

The research not only underscores the diversity in sleep regulation mechanisms among vertebrates but also opens new avenues for understanding the evolution of sleep.

Professor Schier highlighted the significance of these findings. He suggested that exploring the varied control systems evolved in vertebrates could shed light on why some animals are more susceptible to narcolepsy.

The frontier of sleep research: uncharted waters

Dr. Bitsikas further emphasized the potential implications of their research. He noted that fish might hold the key to unraveling the mysteries behind sleep regulation and the vulnerability to sleep-related conditions in different species.

This study challenges existing paradigms and presents a new perspective on sleep regulation. It not only expands our understanding of sleep in the animal kingdom but also paves the way for novel approaches to studying and treating sleep disorders in humans.

A wake-up call for sleep science

The insights garnered from these aquatic studies serve as a beacon, illuminating the vast and unexplored depths of sleep science.

The findings from Professor Schier’s team challenge us to reconsider what we thought we knew about sleep, promising a future where the mysteries of slumber are finally unraveled.

More about sleep regulation 

Sleep regulation involves a complex interplay of biological systems that control when we sleep and wake. This process is primarily governed by two main systems: the circadian rhythm and the sleep-wake homeostasis.

Circadian rhythm

This is our internal clock, which operates on roughly a 24-hour cycle. It’s influenced by external cues like light and darkness, which signal our brain to produce hormones that affect sleep. Melatonin, often called the “sleep hormone,” increases in the evening to promote sleep and decreases in the morning to help wake us up.

Sleep-wake homeostasis

This system keeps track of our need for sleep based on how long we’ve been awake. The longer you’re awake, the stronger your need for sleep becomes, due to the buildup of sleep-inducing substances in the brain, such as adenosine. Sleep reduces these substances, helping to wake us feeling refreshed.

The interaction between these two systems helps regulate our sleep patterns, ensuring we get the rest we need for optimal health and functioning. Disruptions to either system can lead to sleep disorders, such as insomnia or circadian rhythm sleep-wake disorders.

Maintaining regular sleep schedules, managing light exposure, and practicing good sleep hygiene are important for supporting healthy sleep regulation.

The full study is published in the journal Current Biology.

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