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Childhood maltreatment and neglect leads to a wide range of mental disorders highlighted by hormone and immune alterations in neglected children. This social-health challenge leads to the creation of early stress models such as maternal separation (MS) in rodents. We performed a MS model (4h per day, 21) (n=16 MS and n=16 control), and then measured three parameters in male rat adult brains, in order to look for long-term effects: GFAP-positive cells, which indicate astroglial changes, and Iba-1-positive cells, which inform us about reactive microglia and interleukin determination (IL-6, TNFα). These measurements were performed in prefrontal cortices, striatal areas, and the dorsal hippocampus. We found that MS produces a dramatic and sustained decrease in the astroglial population in all the areas measured, whereas microglial changes are more specific to striatal areas.

Subjects' early life events will affect them later in life. When these events are stressful, such as child abuse in humans or repeated maternal separation in rodents, subjects can show some behavioral and brain alterations. This study used young adult female Wistar rats that were maternally raised (AFR), maternally separated from post-natal day (PND) 1 to PND10 (MS10), or maternally separated from PND1 to PND21 (MS21), in order to assess the effects of maternal separation (MS) on spatial learning and memory, as well as cognitive flexibility, using the Morris Water Maze (MWM). We performed quantitative cytochrome oxidase (COx) histochemistry on selected brain areas in order to identify whether maternal separation affects brain energy metabolism. We also performed c-Fos immunohistochemistry on the medial prefrontal cortex (mPFC), thalamus, and hippocampus to explore whether this immediate early gene activity was altered in stressed subjects. We obtained a similar spatial learning pattern in maternally raised and maternally separated subjects on the reference memory task, but only the controls were flexible enough to solve the reversal learning successfully. Separated groups showed less c-Fos activity in the mPFC and less complex neural networks on COx.

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