Enriched environment experience overcomes the memory deficits and depressive-like behavior induced by early life stress

Stress in early life is believed to cause cognitive and affective disorders, and to disrupt hippocampal synaptic plasticity in adolescence into adult, but it is unclear whether exposure to enriched environment (EE) can overcome these effects. Here, we reported that housing rats in cages with limited nesting/bedding materials on postnatal days 2-21 reduced body weight gain, and this type of early life stress impaired spatial learning and memory of the Morris water maze and increased depressive-like behavior of the forced swim test in young adult rats (postnatal days 53-57). Early life stress also impaired long-term potentiation in hippocampal CA I area of slices of young adult rats. Remarkably, EE experience on postnatal days 22-52 had no effect on spatial learning/memory and depressive-like behavior, but it significantly facilitated UP in control rats, and completely overcame the effects of early life stress on young adult rats. These findings suggest that EE experience may be useful for clinical intervention in preventing cognitive and affective disorders during development. (c) 2006 Elsevier Ireland Ltd. All rights reserved.