Gene expression in the hippocampus of behaviorally stimulated rats: analysis by DNA microarray.

Gene expression in the hippocampus of rats exposed to a brief vigorous swimming task was analyzed by DNA microarray hybridization against 5184 known DNA sequences. Each of 12 rats consistently expressed 17% of the genes probed on the microarrays. Transcripts from genes for energy metabolism, development and differentiation, and gene regulation were expressed in the hippocampus to the highest degree relative to their availability on the microarray. The number of genes that were differentially expressed in behaviorally stimulated compared to undisturbed rats was estimated at 2.7% of all expressed genes. Behavioral effects were relatively greater on expression of genes for control of the cell cycle and apoptosis, development and differentiation, protein processing and gene regulation. The magnitude of differential expression due to behavioral stimulation was lower than that generally reported for developmental processes and disease states. Thus the impact of acute behavioral stimulation on steady-state levels of gene expression was small, but (with four replicates per condition) detectable at a statistically significant level. The effects of behavioral stimulation on transcription may thus involve changes in the expression of a relatively small number of genes to a low but reproducible degree.