(24) Neuroplasticity induced by voluntary exercise: Quantifying cell proliferation in the brain and small intestine of adult female mice

     A critical physiological process is the body’s ability to produce new cells, called cell proliferation. This process contributes importantly to tissue growth and differentiation during development, but is less... [ view full abstract ]

     A critical physiological process is the body’s ability to produce new cells, called cell proliferation. This process contributes importantly to tissue growth and differentiation during development, but is less widespread during adulthood. Until recently, little evidence suggested that the mammalian brain was capable of making new neurons (neurogenesis) into adulthood. However, compelling evidence now demonstrates that the adult brain continuously forms new neurons and that the production and survival of these new cells can be influenced by behavioral and environmental factors. Specifically, in rodents, voluntary exercise increases the production and survival of new neurons in the dentate gyrus of the hippocampus, a brain region crucial for learning and memory. Enriched environments that contain polysensory activities and stimuli (e.g., toys, burrows) may also increase the survival of new neurons. The present study investigated the extent to which voluntary exercise and environmental enrichment impact neurogenesis in the adult brain of female mice. We hypothesized that mice living in enriched environments with running wheel access would show more neurogenesis in the dentate gyrus than mice living in standard cages, but that both groups would have similar numbers of new cells in the intestinal epithelia, a control region. Female mice were assigned to live in either an enriched environment (n=14) or standard cage (n=14). The enriched environments contained a running wheel, a soft burrow, novel foods each day, and 2-3 toys that were rotated regularly. The standard cages contained bedding and chow. Bromodeoxyuridine (BrdU), a synthetic thymidine analog that is readily incorporated into the DNA of dividing cells, was added to females’ water bottles (0.8mg/ml) to label dividing cells. After 10 days, mice were sacrificed and brains (n=28) and small intestine (n=6) collected and post-fixed in neutral-buffered formalin. After four days, brains were transferred to sucrose, then were frozen and sectioned using a cryostat, while small intestines were sectioned using paraffin histology. BrdU-labeled cells detected using immunohistochemical labeling were counted in both the dentate gyrus of the hippocampus and in the intestinal epithelium. This study was designed and data collected/analyzed by PSYC359 and BIOL275 students in Spring 2017.