New Research Suggests Links Between Serotonin and Sleep Pressure

Some studies show that serotonin helps with sleeping, while other studies found that serotonin is generally synthesized when a person is awake. To determine the function of serotonin in sleep, scientists from Caltech focused on a portion of the brain that has the most serotonin-generating neurons.

Read more to learn about the link between serotonin and sleep pressure.

The Research Findings

Serotonin is an essential chemical in the body which is known to influence mood, memory, appetite, cognition, and social behavior. While this compound is also known to affect sleep, previous studies have resulted in conflicting facts as to whether serotonin encourages sleepiness or wakefulness.

A team of Caltech scientists started investigating the raphe nucleus area of the brainstem. The raphe is responsible for producing and releasing serotonin to other regions of the brain. A paper describing the study titled “The Serotonergic Raphe Promote Sleep in Zebrafish and Mice,” is published in the journal, Neuron.

This study was led by the senior postdoctoral scientist, Grigorios Oikonomou of the Prober lab. He used tiny, transparent zebrafish as a model to research sleep. Like humans, zebrafish larvae are diurnal, which means their sleep occurs mostly at night.”

The researchers genetically altered zebrafish to disable the production of serotonin in their raphe. The mutant fish were observed to sleep about half as much as they would usually sleep. The fish also slept significantly less than average when the raphe was fully removed. Dr. Oikonomou explained this phenomenon by saying, “This suggests that serotonin produced by the raphe is necessary for the fish to have normal amounts of sleep.”

In another experiment, zebrafish were altered so that their raphe could get activated by light. When the scientists directed light on the fish, it put them right to sleep. Activating the raphe in fish that did not manufacture serotonin, however, did not affect sleep. The scientists believe that by firing neurons in the raphe, the brain builds up sleep pressure. For example, they found that zebrafish lacking serotonin displayed reduced sleep pressure.

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Conclusion

The researchers found that zebrafish without serotonin as well as mice with removed raphe reveal reduced sleep pressure. While the investigation was done in animal models, the animals’ raphe region and its manufacture of serotonin are identical to human brains. The study can contribute to interpretations of some sleep-related side effects of standard antidepressant drugs that improve serotonin levels in the brain.