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Sleep and Behavior in Cross-Fostering Rats: Developmental and Sex Aspects
Olena Santangeli1, Henna Lehtikuja1, Eeva Palomäki1
1Department of Physiology, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
Insights
Mild early-life stress in rats, modeled by cross-fostering, altered sleep patterns and brain chemistry. These changes occurred even without observable behavioral issues, highlighting sleep
Area of Science:
- Neuroscience
- Behavioral Science
- Molecular Biology
Background:
- Adverse early-life events can lead to adult behavioral and sleep disorders.
- Understanding the molecular mechanisms of maltreatment's effects on sleep requires valid animal models.
- Cross-fostering (CF) is a potential model for mild early-life stress.
Purpose of the Study:
- To investigate the effects of cross-fostering on behavior, gene expression, and sleep in Wistar rats.
- To explore molecular mechanisms linking early-life stress to adult sleep changes.
Main Methods:
- Cross-fostering (CF) was used to model mild early-life stress in male and female Wistar rats.
- Behavioral tests, BDNF gene expression analysis (basal forebrain, cortex, hypothalamus), spontaneous sleep, sleep homeostasis, and basal extracellular adenosine levels in the basal forebrain were assessed.
Main Results:
- CF rats showed increased REM sleep onsets and increased total REM and NREM sleep duration during the light period.
- Basal adenosine levels in the basal forebrain were lower in CF rats compared to controls.
- No significant behavioral changes were observed in CF rats.
Conclusions:
- Early-life stress, even when mild and not causing overt behavioral issues, leaves molecular changes in the brain.
- Sleep patterns are sensitive indicators of early-life stress.
- Altered brain chemistry and sleep regulation may represent a vulnerability for later-life psychopathologies.
Study Objective:
Adverse early-life events induce behavioral psychopathologies and sleep changes in adulthood. In order to understand the molecular level mechanisms by which the maltreatment modifies sleep, valid animal models are needed. Changing pups between mothers at early age (cross-fostering) may satisfyingly model adverse events in human childhood.
Methods:
Cross-fostering (CF) was used to model mild early-life stress in male and female Wistar rats. Behavior and BDNF gene expression in the basal forebrain (BF), cortex, and hypothalamus were assessed during adolescence and adulthood. Spontaneous sleep, sleep homeostasis, and BF extracellular adenosine levels were assessed in adulthood.
Results:
CF rats demonstrated increased number of REM sleep onsets in light and dark periods of the day. Total REM and NREM sleep duration was also increased during the light period. While sleep homeostasis was not severely affected, basal level of adenosine in the BF of both male and female CF rats was lower than in controls. CF did not lead to considerable changes in behavior.
Conclusions:
Even when the consequences of adverse early-life events are not observed in tests for anxiety and depression, they leave a molecular mark in the brain, which can act as a vulnerability factor for psychopathologies in later life. Sleep is a sensitive indicator for even mild early-life stress.
