Stress-induced conditions are associated with impaired cerebral blood flow (CBF) and increased risk of dementia and stroke. However, these conditions do not develop in resilient humans and animals. Here the effects of predator stress (PS, cat urine scent, ten days) on CBF and mechanisms of CBF regulation were compared in PS-susceptible (PSs) and PS-resilient (PSr) rats. Fourteen days post-stress, the rats were segregated into PSs and PSr groups based on a behavior-related anxiety index (AI). CBF and its endothelium-dependent changes were measured in the parietal cortex by laser Doppler flowmetry. The major findings are: (1) PS susceptibility was associated with reduced basal CBF and endothelial dysfunction. In PSr rats, the basal CBF was higher, and endothelial dysfunction was attenuated. (2) CBF was inversely correlated with the AI of PS-exposed rats. (3) Endothelial dysfunction was associated with a decrease in eNOS mRNA in PSs rats compared to the PSr and control rats. (4) Brain dopamine was reduced in PSs rats and increased in PSr rats. (5) Plasma corticosterone of PSs was reduced compared to PSr and control rats. (6) A hypercoagulation state was present in PSs rats but not in PSr rats. Thus, potential stress resilience mechanisms that are protective for CBF were identified.

For the first time in modeling posttraumatic stress disorder (PTSD), we have described the morphofunctional state of adrenal glands in Wistar rats resistant and sensitive to predator stress (rodent fear of the predator). Despite the evident signs of adrenal dysfunction in both phenotypes, we have discovered the thickening of undifferentiated cell zone and high indices of functional activity of stem cells in resistant animals, suggesting ample adaptation. The most important data demonstrate the direct relationship between the reduction of corticosterone and testosterone levels and adrenal dysfunction in PTSD models. The study results allow considering the adrenal stem cells as potential therapeutic targets.

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