Primate Early Life Stress Leads to Long-Term Mild Hippocampal Decreases in Corticosteroid Receptor Expression

Background: Expression of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) genes are moderately reduced in several brain regions in depression. These reductions could be partly due to early life stress (ELS), which predicts emotional disorders. Controlled primate studies are important to test whether ELS sufficient to induce long-term emotional changes also induces long-term altered MR and/or GR brain expression. Methods: In the common marmoset, ELS of daily 30-120-min social isolation across month-1 resulted in some long-term changes in homeostasis and emotional behavior. In some of these same subjects, the aim of this study was to use marmoset-specific riboprobes to determine whether ELS produced long-term effects on brain MR and GR gene expression. Results: At adolescence, relative to control subjects, ELS marmosets exhibited mildly reduced messenger RNA signal for both MR (-15%, p = .05) and GR (-13%, p = .02) in hippocampus-primarily CA1-2-but not in prefrontal cortex, other cortical regions, or hypothalamus. Conclusions: In adolescent marmoset monkey brains, reduced hippocampal expression of MR and GR are consistent chronic-indicators of ELS. It is unlikely that these chronic, mild, specific reductions were acute-mediators of the observed long-term emotional effects of ELS. However, they do suggest involvement of hippocampal MR/GR in the neurodevelopmental effects of ELS.