C-FOS IS COORDINATELY EXPRESSED IN NEURONAL AND GLIAL POPULATIONS IN RATS EXPOSED TO ACUTE AND CHRONIC STRESS

The brain´s response to stress involves complex cellular interactions. This study aimed to phenotypically characterize cellular activation in response to acute and chronic stress, using immunoreactivity for the c-Fos protein (c-Fos+) as a specific marker. The objective was to differentially identify neuronal and glial activation in key neuroanatomical regions implicated in stress response regulation. Methods: A varied heterotypic stress model was employed in adult male Wistar rats, applied in acute (2 hours) and chronic (14 days) paradigms. c-Fos immunoreactivity was assessed through immunohistochemical staining. Phenotypic identity (neurons and glial cells). Was determined using double immunofluorescent labeling with specific antibodies (NeuN, GFAP, Iba-1, NG2, Olig-2). Quantitative analyses were performed in Stress-sensitive brain regions. Results: Exposure to stress induced a significant increase under acute exposure conditions in all brain regions examined. Although the neurons showed the highest proportion of c-Fos+ cells, a strong and phenotypically diverse glial activation was also observed, with significant increases in astrocytes, microglia, NG2 cells, and oligodendrocyte lineage cells. Under chronic stress, a significant attenuation of both neuronal and glial activation was observed compared to the acute response; nevertheless, c-Fos levels in most populations and regions remained significantly elevated relative to baseline. Conclusion: c-Fos immunodetection constitutes an effective marker for identifying region-specific cellular activation induced by stress. These findings demonstrate a coordinated response involving neurons as well as multiple glial phenotypes, particularly pronounced under acute stress conditions. The attenuation observed after 14 days of exposure suggests maladaptive responses or differential adaptive processes among cellular populations and neuroanatomical circuits.