Stress-Related Brain Cell Activation Associated with Inadequate Sleep

People who experience stress may wake up during the night more often, and a recently discovered brain circuit in mice may help to explain why. If humans have a comparable route, this could open up new avenues for enhancing the quality of our sleep.

Stress increases the brief arousals from sleep that are natural. People rarely remember these fleeting awakenings since they last less than 20 seconds. However, they have been connected to a host of problems, such as daily weariness, low mood, and cognitive impairment.

It examined the brain activity of sleeping mice in order to comprehend why stress disrupts sleep. First, scientists observed the activity of neurons in 21 mice’s preoptic area of the hypothalamus, a part of the brain essential for controlling sleep. They discovered that only neurons expressing the protein vesicular glutamate transporter 2, or VGLUT2, were active in this area during brief awakenings.

The rats’ stress levels were subsequently increased by the researchers by confining them in cages with hostile mice. These same neurons showed increased activity afterward, which was consistent with the mice waking up more frequently than they had previously.

Lastly, the group used optogenetics—a method of turning on and off cells with light—to suppress these VGLUT2 neurons in 13 stressed mice. When compared to 14 mice whose neurons were not turned off, the average number of short awakenings in these animals was reduced by a third.

All of these results point to the possibility that stress interferes with sleep by stimulating VGLUT2 neurons in the hypothalamic preoptic region.

“Even though our sleep is slightly different from rodents, deep down, we have some shared properties, and [brief awakenings] are one of them,” says Alban Latremoliere at Johns Hopkins University in Maryland. Understanding why these brief awakenings occur, especially in response to stress, could help us improve our sleep quality, he says.

However, he notes that it is unknown if other stressful events also have an impact on this route because this study solely evaluated social stress. It’s still unclear if deactivating these neurons will have any unfavorable repercussions.