Stress-triggered sleep may help mice cope with later anxiety

Summary: Study reveals how stress can induce sleep in mice and how this stress-induced sleep can help reduce anxiety the next day.

Source: imperial college london

Stress stimulates a kind of sleep in mice that then relieves anxiety, according to new research that also identifies the mechanism responsible.

Since sleep is similar in mammals, it is likely that the same mechanism is triggered in the human brain. Discovery of the mechanism could lead to artificial ways to enhance its effects, helping to treat persistent stress disorders such as PTSD.

We often think of stress keeping us up at night, but some types of stress actually seem to induce sleep. Now, a study by researchers from Imperial College London and institutions in China has uncovered how this happens in the brains of mice.

In addition to finding out how sleep is induced, they reported that the sleep the mice experienced seemed to reduce their level of anxiety the next day. The results are published today in the journal Science.

There are two main types of sleep that we, and all mammals, experience: REM (rapid eye movement, where we tend to dream) and non-REM (NREM; deeper, dreamless sleep). People with PTSD experience less REM sleep, which contributes to the theory that REM sleep helps us deal with difficult emotions and stress.

Lead researcher Professor Bill Wisden, from Imperial’s Department of Life Sciences, said: “Our findings add weight to the idea that REM sleep helps us cope with stress. However, we previously only knew about ways to reduce REM sleep, such as certain medications that suppress it.

“Now our study has revealed a mechanism by which REM sleep is induced, paving the way for drugs or other interventions that target the right neurons and boost the anti-stress power of sleep.”

The researchers caused a type of psychosocial stress in mice called “social defeat,” which is used as an analog to human bullying. The mice were exposed to particularly aggressive mice (without physical harm), after which the researchers noted that “flight or fight” hormones rose in their blood, indicating stress.

When the mice slept, the researchers monitored the activity of their neurons (brain cells). This revealed a specific set of neurons that sensed and responded to stress hormone levels and induced elevated sleep in both NREM and REM.

The activity of these neurons and the levels of NREM and REM sleep remained elevated for approximately five hours of sleep, during which time they also sent signals to other neurons that regulate stress hormones, preventing them from releasing them. release more.

Circuits in the brain can induce restful sleep that protects against further anxiety. Credit: Imperial College London

The newly discovered neurons thus not only detected stress and induced sleep accordingly, but also triggered the decline in stress hormones.

Once the mice were awake, the researchers tested their anxiety response, to see how sleep affected their stress behaviors. To do this, they measured the time the mice spent in the light, rather than seeking out the dark, as they tend to do more when anxious.

Their responses were compared to stressed mice that were either sleep-deprived (stimulated by objects) or had their newly identified neurons impaired, meaning they didn’t get the restorative sleep of normal mice.

The mice that didn’t have their stress-induced sleep spent significantly more time in the dark, indicating they were more anxious, and their stress hormone levels remained elevated.

Having found this new mechanism, the team now hopes to find ways to selectively target the responsible neurons to increase their positive effects via sleep.

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The team was funded by the Wellcome Trust and the UK Dementia Research Institute. A diagnosis of dementia can cause significant psychological stress, and the team hopes that if their research can lead to a way to enhance the effects of sleep, it will also help people cope with a new diagnosis. People with dementia also experience more emotional turmoil, and improving REM sleep can also help reduce this distress.

About this sleep and psychology research news

Author: Hayley Dunning
Source: imperial college london
Contact: Hayley Dunning – Imperial College London
Image: Image is credited to Imperial College London

Original research: Access closed.
“A specific circuit in the midbrain detects stress and induces restful sleep” by Bill Wisden et al. Science


A specific circuit in the midbrain senses stress and induces restful sleep

In mice, social defeat stress (SDS), an ethological model of psychosocial stress, induces sleep. Such sleep could enable resilience, but how stress promotes sleep is unclear.

Activity-dependent labeling revealed a subset of the ventral tegmental zone γ-aminobutyric acid (GABA)–somatostatin (VTAVgat-Sst) that sense stress and induce non-rapid eye movements (NREM) and REM sleep through the lateral hypothalamus and also inhibit the release of corticotropin-releasing factor (CRF) in the paraventricular hypothalamus.

Transient stress enhances VTA activityVgat-Sst cells for several hours, allowing them to exert their sleep effects persistently. VTA lesionVgat-Sst cells abolished SDS-induced sleep; without it, anxiety and corticosterone levels remained elevated after stress. Thus, a specific circuit allows animals to restore mental and bodily function while sleeping, potentially offering a refined pathway to treat anxiety disorders.

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