P054 Neurotransmitters of Sleep and Wake in Flatworms

Abstract Introduction Sleep is something that we all do, regardless of how much or how little. But why we sleep, and how sleep evolved is still something of a mystery. This research investigated how neurotransmitters and pharmaceuticals commonly seen in mammalian sleep and wake, play a role in the sleep of free-living flatworms. Methods Using behavioural methods, I observed the behaviour of flatworms under a 12:12 LD lighting condition. Using seven neurotransmitters and one pharmaceutical, I used a novel “yolk and soak” method – feeding the animals the neurotransmitter via hard-boiled egg yolk, as well as bathing them in the same concentration of neurotransmitter, to modulate their behaviour to either induce sleep, or wakefulness. Results We found that GABA, dopamine and histamine appear to be evolutionarily conserved. By dosing the flatworms with these neurotransmitters, we saw that the behaviour changed toward sleep (GABA) or wakefulness (dopamine and histamine) as it does in more recently evolved mammals. We also saw that the H1 antagonist Pyrilamine induced sleep, as it does in other animals. Discussion Understanding how neurotransmitters involved in sleep and wake in humans, and other mammals, may work in animals that are neurologically simple, and older in evolution can lead to many opportunities. We now know that GABA, dopamine and histamine promote sleep and wake in animals that have lost most of their complex systems through secondary simplification, suggesting that these neurotransmitters might be key to the origin of sleep, and may help to understand sleep disorders in humans.