Abstract
There is a tight association between mood and sleep as disrupted sleep is a core feature of many mood disorders. The paucity in available animal models for investigating the role of sleep in the etiopathogenesis of depression-like behaviors led us to investigate whether prior sleep disturbances can predict susceptibility to future stress. Hence, we assessed sleep before and after chronic social defeat (CSD) stress. The social behavior of the mice post stress was classified in two main phenotypes: mice susceptible to stress that displayed social avoidance and mice resilient to stress. Pre-CSD, mice susceptible to stress displayed increased fragmentation of Non-Rapid Eye Movement (NREM) sleep, due to increased switching between NREM and wake and shorter average duration of NREM bouts, relative to mice resilient to stress. Logistic regression analysis showed that the pre-CSD sleep features from both phenotypes were separable enough to allow prediction of susceptibility to stress with >80% accuracy. Post-CSD, susceptible mice maintained high NREM fragmentation while resilient mice exhibited high NREM fragmentation, only in the dark. Our findings emphasize the putative role of fragmented NREM sleep in signaling vulnerability to stress.
Highlights
Global sleep problems are on the rise and negatively impact the quality of life and health, leading to chronic diseases including mood disorders
During the Dark For 15 days, C57BL/6J mice were exposed to daily physical aggression from a novel CD1 aggressor mice for 10 min followed by 24-h psychological aggression since the test mice were kept in the same cage but separated with a perforated plexiglass divider from the aggressor (Figure 1A)
chronic social defeat (CSD)-exposure led to the grouping of the mice into susceptible and resilient phenotypes, based on their social avoidance behavior that was assessed on day 16 via the social interaction (SI) test
Summary
Global sleep problems are on the rise and negatively impact the quality of life and health, leading to chronic diseases including mood disorders. Sleep impairments are among the core symptoms of many stress-induced psychiatric disorders such as depression and anxiety (Hefti et al, 2013; Difrancesco et al, 2019). Among individuals suffering from depression, insomnia and hypersomnia are the most prevalent sleep disorders (Nutt et al, 2008) where common symptoms that affect sleep quality include prolonged sleep latency, difficulty maintaining sleep and early morning awakenings (Steiger and Kimura, 2010). These observations highlight the complex inter-relationship between mood and sleep as sleep disturbances are both symptoms of and a risk factor for mood disorders. Some evidence suggests that slow wave activity (SWA) leads to synaptic downscaling
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