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

The present study examined whether housing in an enriched environment affec ts hippocampal function in responding to the challenge of a spatial water m aze task in naive rats and following transient global ischemia. The enriche d-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-immunos taining in ischemic and sham-operated rats 3 h after water maze testing. Ra ts housed in an enriched environment had an increased number of Fos-positiv e neurons per section in the granule cell layer of the dentate gyrus compar ed to rats housed individually in standard cages. This increase was observe d in both ischemic and sham-operated rats. The experimental groups showed n o differences in the number of Fos-positive cells in different hippocampal areas when the rats were placed in the enriched environment for the same pe riod without the learning task. These results suggest that the number of ne urons responding with altered gene expression in the dentate gyrus is incre ased in rats housed in an enriched environment following training in a wate r maze task. The altered gent: expression is also preserved in ischemic rat s. (C) 2001 Elsevier Science Ltd. All rights reserved.