Early and Later Life Stress Alter Brain Activity and Sleep in Rats

Abstract

Exposure to early life stress may profoundly influence the developing brain in lasting ways. Neuropsychiatric disorders associated with early life adversity may involve neural changes reflected in EEG power as a measure of brain activity and disturbed sleep. The main aim of the present study was for the first time to characterize possible changes in adult EEG power after postnatal maternal separation in rats. Furthermore, in the same animals, we investigated how EEG power and sleep architecture were affected after exposure to a chronic mild stress protocol. During postnatal day 2–14 male rats were exposed to either long maternal separation (180 min) or brief maternal separation (10 min). Long maternally separated offspring showed a sleep-wake nonspecific reduction in adult EEG power at the frontal EEG derivation compared to the brief maternally separated group. The quality of slow wave sleep differed as the long maternally separated group showed lower delta power in the frontal-frontal EEG and a slower reduction of the sleep pressure. Exposure to chronic mild stress led to a lower EEG power in both groups. Chronic exposure to mild stressors affected sleep differently in the two groups of maternal separation. Long maternally separated offspring showed more total sleep time, more episodes of rapid eye movement sleep and higher percentage of non-rapid eye movement episodes ending in rapid eye movement sleep compared to brief maternal separation. Chronic stress affected similarly other sleep parameters and flattened the sleep homeostasis curves in all offspring. The results confirm that early environmental conditions modulate the brain functioning in a long-lasting way.

Sleep and Behavior in Cross-Fostering Rats: Developmental and Sex Aspects

“…31 Some studies also reported changes in NREM sleep. 29,31,32 In the present study, although the cross-fostering model deviates from the maternal separation, the results were analogous: REM sleep onsets during spontaneous sleep were increased in both male and female CF treated rats in light and dark periods. Moreover, the total amount of time spent in REM and NREM sleep during the light period was elevated in CF males and females, which was reflected as a decrease in waking.…”

“…[29][30][31][32][33][34] The core of the reported, slightly variable, separation protocols is a daily separation of the pups from their mothers for 180 min during a period of several days at the age of 2-14 (16) days. This procedure inflicts considerable stress, as evidenced by hyper responsivity of the hypothalamicpituitary-adrenal axis and increased corticosterone levels in adulthood.…”

Sleep electroencephalography as a biomarker in depression

“…136,137 With exposure to inescapable chronic mild stress, a mouse model that has received early life stress (long maternal separation, otherwise known as LMS) shows different sleep responses. 138 Compared to its control group (brief maternal separation), the power of EEG spectra during both non-REM and REM sleep was significantly lower in the LMS group during recovery after chronic stress. Although the amount of sleep, especially REM sleep, does not differ under baseline condition between these two groups, LMS, which is a sort of chronic stress, leads to increased vulnerability and is detected in sleep EEG.…”

Psychoneuroimmunology of Early-Life Stress: The Hidden Wounds of Childhood Trauma?

“…Fourth, early-life stress has been linked to alcohol and substance abuse disorders and smoking (Dube et al, 2003;Anda et al, 1999), which can increase inflammation levels (Crews et al, 2006;Shiels et al, 2014). Fifth, early-life stress has been associated with decreased total sleep and disruption in sleep architecture in rodents (Feng et al, 2007;Mrdalj et al, 2013;Tiba et al, 2004) and humans (Gregory and Sadeh, 2016;Kajeepeta et al, 2015). In turn, clinical experiments have shown that sleep deprivation is associated with an increase in the expression of pro-inflammatory cytokines in humans (Irwin et al, 2006), and epidemiological studies have found that reduced sleep is associated with elevated levels of inflammation biomarkers (Miller et al, 2009).…”