Enriched environment increases myelinated fiber volume and length in brain white matter of 18-month female rats

Abstract

Cognition and memory decline with normal aging, which could be partly attributed to the degeneration of brain white matter. Previous studies demonstrated that exposure to an enriched environment (EE) could protect cognition and memory from aging. However, if or how EE might affect the brain white matter has not been thoroughly investigated. In the current study, 24 middle-aged (14-month-old) female Sprague –Dawley (SD) rats were randomly assigned to EE or standard environment (SE) for 4 months. At the end of the environment intervention, the Morris water maze tests were performed. Then, 5 rats were randomly selected from each group for stereological assessment of the brain white matter and its myelinated fibers. The results revealed that middle-aged rats living in EE displayed better spatial learning than SE controls. The white matter volume was 124.6±7.8mm3 in EE rats, which was significantly enlarged compared with 84.8±3.4mm3 in SE rats. Likewise, the myelinated fiber volume was markedly increased from 56.6±1.7mm3 in SE rats to 87.2±9.0mm3 in EE rats; so was the myelinated fiber length from 83.5±6.6km in SE rats to 119.0±10.0km in EE rats. Our data suggested that EE could protect brain white matter and its myelinated fibers of female rats at middle age.