Reduced resting-state functional connectivity of the basolateral amygdala to the medial prefrontal cortex in preweaning rats exposed to chronic early-life stress
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Early-life stress (ELS) exposure has long-term consequences for both brain structure and function and impacts cognitive and emotional behavior. The basolateral amygdala (BLA) plays an important role in anxiety and fear conditioning through its extensive anatomical and functional connections, in particular to the medial prefrontal cortex (mPFC). However, how ELS affects amygdala function and connectivity in developing rats is unknown. We used the naturalistic limited bedding/nesting (LB) paradigm to induce chronic stress in the pups between postnatal day (PND) 1–10. Male normal bedding (NB, control) or LB offspring underwent structural and resting-state functional MRI (rs-fMRI) on PND18 and in adulthood (PND74–76). Adult male rats were tested for fear conditioning and extinction behavior prior to scanning. Seed-based functional connectivity maps were generated based on four BLA seeds (left, right, anterior and posterior). At both ages, LB induced different effects on anterior and posterior BLA networks, with significant reductions in rs-fMRI connectivity between the anterior BLA and mPFC in LB compared to NB offspring. BLA connectivity was lateralized by preweaning age, with the right hemisphere displaying more connectivity changes than the left. Weak negative volumetric correlations between the BLA and mPFC were also present, mostly in preweaning LB animals. rs-fMRI connectivity and volumetric changes were associated with enhanced fear behaviors in adult LB offspring. Activation of the LB-exposed neonatal amygdala described previously might accelerate the maturation of BLA–mPFC projections and/or modify the activity of reciprocal connections between these structures, leading to a net reduction in rs-fMRI connectivity and increased fear behavior.
KeywordsBasolateral amygdala Resting-state connectivity Neonatal stress Medial prefrontal cortex Preweaning Imaging Volumetry Behavior
We thank Dr Jürgen Germann and Ms Elisa Guma (Douglas Institute, Imaging Center) for their assistance with the Display software package for manual segmentation analyses and preliminary co-registration analyses, respectively.
This study was funded by an NSERC Grant to CDW (Grant #138199) and an internal McGill-Faculty of Medicine studentship award to AG.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Research involving animals and ethical approval
All experimental procedures carried out on Sprague–Dawley rats were approved by the University Animal Care Committee at McGill University in accordance with the guidelines of the Canadian Council on Animal Care.
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