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In utero exposure to valproic acid changes sleep in juvenile rats: a model for sleep disturbances in autism
Insights
Valproic acid exposure in rats disrupts sleep patterns, increasing wakefulness and altering brain activity, mirroring autism spectrum disorder (ASD) symptoms. This model offers insights into the molecular basis of sleep disturbances in ASD.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Sleep Medicine
Background:
- Autism spectrum disorder (ASD) is frequently associated with sleep disturbances.
- Animal models are crucial for understanding the neurobiological underpinnings of ASD and its comorbidities.
- The valproic acid (VPA) model is widely used to study ASD, but its impact on sleep requires further investigation.
Purpose of the Study:
- To investigate sleep disturbances in juvenile rats exposed to valproic acid (VPA) in utero.
- To examine sleep behavior, architecture, and electroencephalogram (EEG) spectral characteristics in the VPA model of ASD.
- To assess the expression of glutamic acid decarboxylase (GAD) 65/67, key enzymes in GABA synthesis, in VPA-exposed rats.
Main Methods:
- A comparative study was conducted on juvenile Sprague-Dawley rats exposed to VPA or saline in utero.
- Sleep patterns were monitored using EEG and electromyogram (EMG) recordings.
- EEG spectral analysis and Western blot analysis for GAD 65/67 protein expression were performed.
Main Results:
- VPA-exposed rats exhibited significantly increased wake time and decreased non-rapid eye movement (NREM) sleep during the light phase.
- EEG spectral analysis revealed increased high-frequency activity during wake and REM sleep, and reduced theta power across all vigilance states in VPA-exposed rats.
- Reduced levels of GAD 65 and GAD67 proteins were observed in the cortical tissue of VPA-exposed rats, indicating disruption of the GABAergic system.
Conclusions:
- The VPA model effectively recapitulates sleep disruptions observed in humans with ASD.
- This model provides a valuable tool for investigating the cellular and molecular mechanisms underlying sleep disturbances in ASD.
- Further research utilizing this model can elucidate the role of GABAergic system dysfunction in ASD-related sleep problems.
Study Objectives:
To determine whether sleep disturbances are found in the valproic acid model of autism spectrum disorders (ASD).
Design:
Comparative study for sleep behavior, sleep architecture, electroencephalogram (EEG) spectral analysis, and glutamic acid decarboxylase (GAD) 65/67 protein expression in juvenile rats exposed to valproic acid (VPA), sodium salt, or saline in utero.
Setting:
N/A.
Participants:
Juvenile (postnatal day 32) male and female Sprague-Dawley rats.
Interventions:
In utero exposure to either saline or 400 mg/kg VPA administered intraperitoneally to the dams on gestational day 12.5. On postnatal days 22-24, all rats were implanted with transmitters to record EEG and electromyogram (EMG) activity.
Measurements And Results:
During the light phase, when nocturnal animals are typically quiescent, the VPA-exposed animals spent significantly more time in wake (∼35 min) and significantly less time in non-rapid eye movement (NREM) sleep (∼26 min) compared to the saline controls. Furthermore, spectral analysis of the EEG revelled that VPA-exposed animals exhibited increased high-frequency activity during wake and rapid eye movement (REM) sleep and reduced theta power across all vigilance states. Interestingly, the gamma-aminobutyric acid (GABA)-ergic system, which modulates the induction and maintenance of sleep states, was also disrupted, with reduced levels of both GAD 65 and GAD67 in the cortical tissue of VPA-exposed animals compared to saline controls.
Conclusions:
To date, the current animal models of ASD have been underutilized in the investigation of associated sleep disturbances. The VPA animal model recapitulates aspects of sleep disruptions reported clinically, providing a tool to investigate cellular and molecular dysregulation contributing to sleep disruptions in ASD.
