Effects of Periodic and/or a Single Exposure to an Enriched Environment on Neural C-fos Expression in Adolescent Rats

Environmental enrichment of laboratory animals consists of cognitive, social and physical enhancement of the subjects’ life experiences. Enrichment produces improved performance on memory tasks. In the present study, 16 Long-Evans rats (8 male and 8 female) were randomly assigned to one of four experimental groups on postnatal day 34 (n = 4 for each group). Animals were given periodic exposures to the enriched environment through adolescence, an acute expose just before sacrifice, both periodic and acute enrichment, or no enrichment. Rats were sacrificed on post-natal day 77-79, and 72 sagittal sections (50 µm) were taken from each brain, then processed for visualization of the c-fos protein. There were more c-fos positive neurons in the CA1 region, entorhinal cortex and subiculum of rats that received an acute enriching experience only, compared to controls. Additionally, more c-fos positive neurons were observed within these three structures in rats that only received an acute enriching experience compared to rats that received periodic enrichment and acute enrichment. These findings suggest that, in the mammalian brain, diversity of experience during adolescence produces changes in neural circuitry that may foster improved mental acuity in adulthood.