AbstractAltered activity of corticolimbic brain regions is a hallmark of stress-related illnesses, including mood disorders, neurodegenerative diseases, and substance abuse disorders. Acute stress adaptively recruits brain region-specific functions for coping, while sustained activation under chronic stress may overwhelm feedback mechanisms and lead to pathological cellular and behavioral responses. The neural mechanisms underlying dysregulated stress response and how they contribute to behavioral deficits are poorly characterized. Here, we tested whether prior exposure to chronic restraint stress (CRS) or unpredictable chronic mild stress (UCMS) in mice could alter neuronal response to acute stress and whether these changes are associated with chronic stress-induced behavioral deficits. More specifically, we assessed neuronal activation indexed by c-Fos+ cell counts in 24 stress- and mood-related brain regions, and determined if changes in acute stress-induced neuronal activation were linked to chronic stress-induced behavioral impairments. Results indicated that CRS and UCMS led to convergent physiological and anxiety-like deficits, whereas cognition was impaired only in UCMS mice. CRS and UCMS exposure exacerbated neuronal activation in response to an acute stressor in anterior cingulate cortex (ACC) area 24b and ventral hippocampal (vHPC) CA1, CA3, and subiculum. In dysregulated brain regions, levels of neuronal activation were positively correlated with principal components capturing variance across widespread behavioral alterations relevant to stress-related disorders. Our data supports an association between a dysregulated stress response, altered corticolimbic excitation/inhibition balance, and the expression of maladaptive behaviors.HighlightsChronic stress models produce variable profiles of physiological deficits, anxiety-like behavior, and impaired cognitionAcute stress-induced activation of ACC A24b & vHPC is exacerbated by prior chronic stress exposureIn regions dysregulated by chronic stress, altered neuronal activation is positively correlated with behavioral deficits
Reduced anterior cingulate cortex volume induced by chronic stress correlates with increased behavioral emotionality and decreased synaptic puncta density