Depression-prone mice with reduced glucocorticoid receptor expression display an altered stress-dependent regulation of brain-derived neurotrophic factor and activity-regulated cytoskeleton-associated protein

Increasing evidence suggests that depression is characterised by impaired brain plasticity that might originate from the interaction between genetic and environmental risk factors. Hence, the aim of this study was to investigate changes in neuroplasticity following exposure to stress, an environmental condition highly relevant to psychiatric disorders, in glucocorticoid receptor-deficient mice (GR+/-), a genetic model of predisposition to depression. Specifically, we have analysed the neurotrophin brain-derived neurotrophic factor (BDNF) and the immediateearly gene activity-regulated cytoskeletal-associated protein (Arc), two closely related molecules that can contribute to neuroplastic and morphological changes observed in depression. We found a region-specific influence of the GR-genotype on BDNF levels both under basal and stress conditions. Steady-state levels of BDNF mRNA were unchanged in hippocampus while up-regulated in frontal lobe of GR+/- mice. Following exposure to an acute stress, increased processing from pro-to mature BDNF was observed in hippocampal synaptosomes of wild-type mice, but not in GR mutants. Furthermore, the stress-dependent modulation of Arc was impaired in the hippocampus of GR+/- mice. These results indicate that GR+/- mice show overt differences in the stress-induced modulation of neuroplastic proteins, which may contribute to pathologic conditions that may originate following gene x environment interaction