Effects of Constant Track Running Exercise on the Expression of the Immediate Early Gene Arc in the Rat Hippocampus

Abstract

Arc is an IEG expressed in the CA1 sub-field of the hippocampus, following stimulus from an external environment and is expressed in the place cells involved in spatial learning. An initial experiment showed that Arc expression levels decreased with 25 minute rest periods between sessions. The current study aimed to see if similar results are seen with track running, if the rest periods are removed. The rats ran on a small circular track, ensuring that a small ensemble of place cells activate on each lap. Animals were assigned to 4 groups: positive control for Arc induced by MECS; negative control for animals sacrificed from their home cage; a 5 minute group and a 45 minute group. The brain tissue was stained using FISH. The 45 minute group had a 4% lower Arc expression than the 5 minute group. A univariate ANOVA indicated a statistically significant effect in the main factor of Behavioral Group (F= 6.955, p=0.03). Tukey tests showed that the differences between the MECS and the CC groups (p<0.05) and the MECS and the 45 minute groups (p<0.05) were significant. The behavioral groups showed no statistical significance meaning that massed exposure without rest does not attenuate Arc signal.