Codeluppi, S. A. | bioRxiv Science

bioRxiv2025

Neuronal and Astrocytic Activity Changes Induced by Acute and Chronic Stress

Exposure to acute, repeated, or chronic stress elicits a spectrum of cellular changes ranging from adaptive to maladaptive, including in the prefrontal cortex (PFC) where both neurons and astroglia undergo morphological, cellular and molecular remodeling. However, whether these alterations translate into altered cell activity and neuron-astroglia communication and how such changes evolve with recurrent stress or chronic stress exposure remains poorly understood. To address these questions, we used dual-color in vivo fiber photometry to longitudinally record PFC neuronal and astroglial calcium (Ca{superscript 2}) signals in the same mice during a brief (tail pinch), sustained (immobilization) acute stress, repeated homotypic stress across weeks, and unpredictable chronic mild stress (UCMS), tracking of same cellular network across time. We found that acute stressors elicited coordinated increases in neuronal and astroglial Ca{superscript 2} activity and enhanced their Ca2+ signal coupling. Repeated intermittent stress induced comparable per-cell-type responses but progressively strengthened coupling, suggesting adaptation. We also demonstrated that this trajectory is reversed under UCMS; neuronal Ca{superscript 2} reactivity to stress challenge was sensitized whereas astroglial reactivity was blunted. This was associated with a weakened intercellular coupling (-3.5 fold) and astroglia became progressively hyporesponsive to neuronal drive. UCMS-induced neuron-astroglia functional coupling impairment coincided with the onset of anhedonia- and anxiety-like behavioral deficits. These findings position impaired neuron-astroglial functional coupling as a potential substrate of stress-induced cortical dysfunction that may distinguish adaptive from maladaptive stress responses, offering a mechanistically tractable target for intervention in stress-related psychiatric disease such as depression, where dysfunction in both cell types has been consistently reported.

neuroscience↗

bioRxiv2021

Behavioral and Neurostructural changes associated with Chronic Amygdala Hyperactivation

BackgroundThe amygdala (AMY) is a key brain region of the limbic system that plays a critical role in emotion processing and stress response. Functional magnetic resonance imaging (fMRI) studies identified abnormal AMY activation in psychiatric illnesses including major depressive disorder (MDD). Stress exposure is a major precipitating factor of MDD episodes which are associated with AMY hyperactivity. Preclinical studies using of pharmacologic, opto- and chemogenetic approaches to activate AMY neurons have consistently demonstrated that acute AMY hyperactivation induces anxiety-like behaviors in mice. However, it remains unknown if chronic hyperactivation of the amygdala (cHOA) is sufficient to induce chronic stress-like deficits or is a susceptibility factor for chronic stress-induced behavioral, volumetric and synaptic deficits. MethodsUsing designer receptor exclusively activated by designer drug (DREADD) approach, basolateral amygdala (BLA) neurons of Camk2a-cre mice infected with a virus driving the expression of the Gq-coupled DREADD were activated with clozapine-N-oxide (in drink water for 5 weeks). Mice were then exposed to chronic restraint stress (CRS; 1X/day for 1hr) for 2 weeks. All mice were behaviorally assessed in the Phenotyper (PT), and sucrose consumption tests (SCT) each week and in the novelty supressed feeding (NSF, once at the end of the experiment). Animals were then perfused for ex vivo-MRI and puncta density analysis. ResultsWe found that mice with cHOA displayed a progressive increase in baseline anxiety-like deficits in the PT test and slightly more marked deficits following CRS compared to controls, but not statistically different from animals subjected to CRS alone. Also, cHOA did not exacerbate CRS effect in the NSF. No significant cAH effect was found in the SCT before or after CRS. MRI analysis revealed no statistical charges between groups, while increased synaptic puncta density was found in cHOA mice subjected to CRS compared to cHOA or CRS alone. ConclusionWe demonstrate that cAH is sufficient to induce anxiety and may exacerbate CRS effects on anxiety and synaptic measures. Results also suggest that cHOA was not sufficient to induce depressive-like behavior and was not a vulnerability factor for stress-induced depressive-like behavior in mice. Altogether, our findings imply that a strong causal link between AMY hyperactivity and elevated anxiety, but not depressive-like behaviors and provide critical information to clinical research focused on using AMY activity level as a biomarker in stress-related illnesses.

neuroscience↗