Many people are aware that stress can lead to poor sleep at night. However, scientists have for the first time identified how stress stimulates brain cells at the wrong time during sleep phases, causing interrupted sleep and poor quality rest, according to New Atlas citing the journal Current Biology.
**Physiological Impact**
In investigating the physiological impact of stress on sleep in a mouse model, researchers from the University of Pennsylvania monitored activity in the preoptic area (POA) of the hypothalamus during normal sleep. They discovered that glutamatergic neurons (VGLUT2) are more active during wakefulness and less active during non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep comprises three stages of a 90-minute sleep cycle, with REM sleep being the fourth stage. Each stage contains memory storage functions for the brain and body that are essential for health and memory.
**Minor Disturbances**
However, stress can cause VGLUT2 to become active during NREM phases when it usually is not, resulting in "minor disturbances" that disrupt the regular cycle. When the scientists stimulated the neurons, there was an increase in these minor disturbances. While lack of sleep affects memory, immune function, emotional regulation, and appetite, it is increasingly associated with an elevated risk of disease and mental health issues.
**Sleep Disorders**
Lead researcher Shingai Chong, an assistant professor of neuroscience at the University of Pennsylvania, stated, "When you have a bad night’s sleep, you notice that your memory isn’t as good as usual, or your emotions are all over the place – but a bad night’s sleep disrupts many other processes throughout your body," adding that "this is exacerbated in individuals suffering from stress-related sleep disorders."
**Suppressing Negative Effects**
Researchers believe the new discovery may not address the root cause of the problem, specifically stress, but it reveals significant potential in targeting the regulation of VGLUT2 to suppress these minor disturbances. The researchers think there is particular importance for those suffering from sleep disorders or other conditions such as anxiety and post-traumatic stress disorder (PTSD). Chong added, "It is important to understand the biological factors driving brain activity during these critical stages of sleep and how stressors can disrupt it, so that we may someday develop treatments to help individuals achieve sounder sleep, allowing their minds to complete these important processes."
**Developing New Treatments**
Researchers also found that when they inhibited VGLUT2 neurons, the minor disturbances during NREM sleep decreased as well. The restorative periods of NREM sleep were prolonged. Lead researcher Jennifer Smith noted, "The glutamatergic neurons in the hypothalamus give us a promising target for developing treatments for stress-related sleep disorders," indicating that "the ability to reduce interruptions during the critical stages of NREM sleep by suppressing VGLUT2 activity would be groundbreaking for individuals suffering from sleep disorders due to conditions like insomnia or PTSD."
