Exposure to Enriched Environment Restores Altered Passive Avoidance Learning and Ameliorates Hippocampal Injury in...

The aim of the study was to investigate the effects of exposure to enriched environment (EE) on passive avoidance learning and hippocampal cellular morphology in rats exposed to chronic restraint stress.

Adult male albino Wistar rats were assigned into the following groups: normal control (NC) remained undisturbed in their home cages; stressed group (S) subjected to restrained stress (6 h/day) followed by housing in standard housing for 21 days; And stressed + EE (S + EE) subjected to restrained stress followed by housing in EE for 21 days. On 22^nd day, six animals from each of the three groups were exposed to passive avoidance test. The remaining animals were sacrificed. Hippocampus was isolated and processed for cellular morphology using cresyl violet staining.

Data were analyzed using one-way analysis of variance followed by Tukey's multiple comparison test (post hoc).

Stressed rats exposed to EE showed significant improvement in passive avoidance learning test compared to NC. Quantification of the surviving neurons in the hippocampal subfields and their cellular morphology revealed significant neuroprotection in S + EE in cornu ammonis-2 (CA2) neurons and CA3 hippocampal neurons. No significant changes were found in CA1 hippocampal subfield.

The outcome of this study makes us to think the possibilities of adopting EE as an alternative strategy in brain diseases where there is chronic stress and to minimize the impairment in learning and memory.