Stressful experiences differentially regulate immediate-early genes and stress hormone receptors in immature and mature dentate gyrus neurons

Abstract

Hippocampal functions in memory and emotion are sensitive to stress. Stress and cor- ticosteroids modulate neuronal activity and plasticity in the hippocampus and regulate its contributions to behavior. One feature of the hippocampus that is highly sensitive to stress is adult neurogenesis. Stress alters the proliferation and survival of adult-born neurons in the hippocampal dentate gyrus (DG). Furthermore, adult-born neurons mod- ulate the behavioral response to stress. How newborn neurons respond to stress at a cellular level still remains relatively unexplored, but is important for understanding how they regulate behavioral responses. Here we examined whether two experiences that differ in the degree of stress, novel context exposure and physical restraint, alter levels of immediate-early genes (IEGs), mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) in immature adult-born neurons and putative older neurons in the DG. We found that experience, particularly restraint stress, reduces levels of zif268 and MR in immature neurons but not older neurons. In contrast, both context exposure and restraint stress increased GR levels in immature neurons and mature neurons. These divergent cellular responses suggest that these two neuronal populations may have dis- tinct functions in regulating the stress response.