Chemicals involved in the sleep of seals

Apparently, seals are able to sleep in the water. But only half their brain sleeps at a time in the water. On land, their whole brain sleeps. This article discusses research findings involving two chemicals in the brain involved in seal sleep. Acetylcholine is high in the side of the brain still awake whereas serotonin is equal on both sides. Unfortunately, sleep in humans is still more complex than just these two neurochemicals. Other important ones are orexins, histamine, norepinephrine, and dopamine. But this research may allow sleep scientists to help figure out how the neurochemicals are related and involved in sleep, so that one day we may be able to better understand and treat sleep disorders.