Enriched Environment Exposure
Objective: To assess effects of enriched environment exposure on hippocampal progenitor cell survival and gene expression in mice, with investigation of whether prior running experience primes the hippocampus for enrichment effects
Protocol Steps
Animal acquisition and housing setup
Obtain 40 female C57BL/6 mice, 8 weeks old. Randomly distribute to four experimental groups (N = 10 per group). House all animals in same room with constant 12-hour light/dark cycle. Provide food and water ad libitum.
Note: Female mice used to avoid confounding effects of territorial behavior and social hierarchy development seen in males
View evidence from paper
“Forty female C57BL/6 mice, 8-weeks old at the beginning of the experiment, were obtained from Charles River (Sulzfeld, Germany). The mice were randomly distributed to four experimental groups, N = 10 per group. All animals were kept in the same room with a constant 12-h-light/dark-cycle and were fed with the same food and water ad libitum.”
Phase 1: First 10 days of experimental conditions
Implement first phase conditions for 10 days. RUNENR and RUNSTD groups: provide running wheel access. STDENR and STDSTD groups: standard housing without running wheel.
Note: This phase establishes baseline conditions and primes hippocampus in running groups
View evidence from paper
“The experimental period lasted 45 days, divided into a first phase of 10 days and a second phase of 35 days”
BrdU administration at end of Phase 1
At end of first period (day 10), administer single daily injections of BrdU (50 μg/g body weight in 0.9% saline) to five mice from each group for 3 consecutive days. This labels progenitor cells generated in the last 3 days of phase 1.
Note: Remaining animals (5 per group) were intended for gene expression study which failed technically. BrdU labels cells in S-phase during injection period.
View evidence from paper
“At the end of the first period, five mice of each group received single daily injections of persistent S-phase label bromodeoxyuridine (BrdU; 50 μg/g body weight in 0.9% saline; Sigma) for 3 days.”
Phase 2: Second 35 days of experimental conditions
Implement second phase conditions for 35 days. RUNENR group: enriched environment (no running wheel). RUNSTD group: standard housing (no running wheel). STDENR group: enriched environment. STDSTD group: standard housing.
Note: RUNSTD and RUNENR differ only in phase 2. STDENR and RUNENR differ only in phase 1. This design allows assessment of running priming effects and enrichment effects independently.
View evidence from paper
“The experimental period lasted 45 days, divided into a first phase of 10 days and a second phase of 35 days. RUNSTD and RUNENR differed in the second phase only, not the first. STDENR thus differed only in the first phase, not the second.”
End of experiment analysis
At end of 45-day experimental period, analyze all animals. BrdU-labeled cohort used to assess survival-promoting effects of enrichment stimulus on progenitor cells generated in last 3 days of phase 1.
Note: Measured effects of running in RUNSTD condition represent sustained effects after 35 days of discontinuation of physical exercise
View evidence from paper
“Because all animals were analyzed at the end of the 45 days, the measured effects of running in this condition represented sustained effects after 35 days of discontinuation of physical exercise.”