Enriched-environment housing increases neuronal Fos-staining in the dentate gyrus after a water maze spatial learning...

The present study examined whether housing in an enriched environment affects hippocampal function in responding to the challenge of a spatial water maze task in naive rats and following transient global ischemia. The enriched-environment housing was used for 11 days and was instituted the day after the induction of 20-min ischemia. Thereafter, the rats were tested in the water maze. The function of hippocampal neurons was assessed by Fos-immunostaining in ischemic and sham-operated rats 3 h after water maze testing. Rats housed in an enriched environment had an increased number of Fos-positive neurons per section in the granule cell layer of the dentate gyrus compared to rats housed individually in standard cages. This increase was observed in both ischemic and sham-operated rats. The experimental groups showed no differences in the number of Fos-positive cells in different hippocampal areas when the rats were placed in the enriched environment for the same period without the learning task. These results suggest that the number of neurons responding with altered gene expression in the dentate gyrus is increased in rats housed in an enriched environment following training in a water maze task. The altered gene expression is also preserved in ischemic rats.