Amalie Aasvang

Abstract

The postnatal period is important for normal brain development across species, and environmental manipulations during this period have been shown to have significant impact on sleep later in life. The main aim of this study was to investigate the effect of early life stress and chronic mild stress (CMS) in adulthood on sleep and wakefulness, and further to investigate how sleep and wakefulness were affected by different individual mild stressors. Male, newborn rats (Wistar rats, n = 13) were exposed to brief-maternal separation (BMS, 10 min daily) and long-maternal separation (LMS, 3 h daily) during postnatal day 2-14. In adulthood, all animals were exposed to 4 weeks of (CMS). Electroencephalography (EEG) and electromyography (EMG) were recorded continuously during 24 h baseline and one week during the CMS protocol to assess sleep and wakefulness. Results showed no overall effect of early life stress on sleep and wakefulness in either active phase or in inactive phase, as LMS and BMS offspring displayed similar time in wakefulness, slow wave sleep (SWS) and rapid eye movement (REM) sleep. CMS exposure affected sleep and wakefulness in both LMS and BMS offspring. One week of CMS exposure affected sleep and wakefulness similarly in LMS and BMS offspring. Across all CMS days during active phase, wakefulness was reduced and SWS, REM sleep and total sleep time were increased, whereas during inactive phase, wakefulness was increased and SWS, REM sleep and total sleep time were reduced. Stressors “food deprivation” and “social stress” induced a stronger effect in LMS compared to BMS offspring. During food deprivation LMS offspring showed less wakefulness and more total sleep time compared to BMS offspring. After exposure to social stress the LMS offspring spent more time in wakefulness, less time in SWS and had less total sleep time compared to BMS offspring. Overall, these findings suggest a difference in stress reactivity in LMS and BMS offspring and add to the literature on the consequences of early life stress in combination with chronic mild stress in adulthood on sleep and wakefulness, both during active and inactive phase

This master`s project was a part of the project: The early life condition – A translational study of affective and behavioral outcomes and genetic modulation.

Supervisor
Main supervisor Jelena Mrdalj