Impact of enriched-environment housing on brain-derived neurotrophic factor and on cognitive performance after a transient global ischemia.

Environmental enrichment promotes structural and functional changes in the brain, including enhanced learning and memory performance in rodents. Transient global cerebral ischemia (15 min) causes specific damage to dorsal hippocampal area CA1 pyramidal cells of the rat concomitantly with cognitive deficits. Thus, we investigated if environmental enrichment can protect rats against the cognitive and neurological consequences of transient ischemia. We evaluated the impairment of learning and memory with three tasks: odour discrimination, object exploration and spatial learning. Contrary to expectation, we found that the enriched environment improved performances for both ischemic and sham rats in odour discrimination and object exploration tasks compared with standard condition housed rats. After exposure to an enriched environment, ischemic rats performed better in the water maze than those in the standard housing conditions. However, exposure to an enriched environment does not protect against actual loss of CA1 pyramidal cells. Brain-derived neurotrophic factor (BDNF) levels were increased in environmental enrichment animals compared to those housed in standard conditions. We conclude that environmental enrichment has positive effects that are independent of the effects of ischemic brain lesions. Copyright 2003 Elsevier B.V.