Linking serotonin, REM sleep, the habenula and depression


All mammals, birds and insects sleep. Still we know very little about how sleep is regulated by the brain.

According to a new study, a brain region called the lateral habenula plays a central role in REM sleep.

In an article published in the Journal of Neuroscience, a research team shows that the lateral habenula maintains and regulates REM sleep in rats through regulation of the serotonin system. This is the first time the lateral habenula has been linked to serotonin metabolism and sleep.

The habenula is key to sleep regulation

The lateral habenula is the part of the brain which regulates the metabolism of the neurotransmitter serotonin and plays a key role in cognitive functions.

“Serotonin plays a central role in the pathophysiology of depression; however, it is not clear how abnormalities in regulation of serotonin metabolism in the brain lead to symptoms such as insomnia in depression,” explained Drs. Hidenori Aizawa and Hitoshi Okamoto, who led the study from the RIKEN Brain Science Institute.

REM sleep reduced when the habenula was impaired

The researchers showed that by removing the lateral habenula in rats, the rats experienced a reduction of theta rhythm – an activity that happens during REM sleep – and the REM sleep periods were shortened.

“Our results indicate that the lateral habenula is essential for maintaining theta rhythms in the hippocampus, which characterize REM sleep in the rat, and that this is done via serotonergic modulation,” said Aizawa. “The study reveals a novel role of the lateral habenula, linking serotonin and REM sleep, which suggests that an hyperactive habenula in patients with depression may cause altered REM sleep.”

Source: MedicalNewsToday, Journal of Neuroscience

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