Exercise has been shown to increase neurogenesis, while stress has been shown to decrease neurogenesis in the hippocampus. This region of the brain is important for memory.
In an experiment to determine whether exercise during periods of stress can negate the deleterious effects of stress on neuron renewal in the hippocampus, two groups of rats were chronically injected with corticosterone, the adrenal stress hormone in rodents, and one group exercised, while the other group did not exercise. Two additional control groups were included that did not receive corticosterone, and one exercised, while the other did not. In addition, to determine whether age influences the ability of exercise to alleviate stress-effects on neurogenesis both young (6 weeks old) and old (52 weeks old) rats were included in the study.
After 4 weeks, rats were injected with bromodeoxyuridine (BrdU), a substance that is incorporated into DNA in replicating cells and can be visualized by immunocytochemistry. Below is a micrograph of BrdU-labeled nuclei (red) in neurons with neurofilaments also labeled (green).
Brains were prepared for BrdU localization in neurons twenty-four hours after BrdU application. BrdU-labeled neurons were counted in sections of the hippocampus. The average number of labeled neurons per square 100 microns was recorded for each group of rats. The data are shown in the graph below.
From the results of this study, which of the following are logical deductions regarding stress and exercise? Select ALL that apply.