Running coordinately upregulates hippocampal BDNF and GAD67 expression in Long‐Evans rats

To elucidate the effects of wheel‐running exercise on hippocampal inhibition, male Long‐Evans rats were housed with or without access to running wheels for thirty days. We then assessed hippocampal expression of glutamic acid decarboxylase‐67 (GAD67), an enzyme involved in synthesis of the inhibitory neurotransmitter GABA, using in situ hybridization. Four weeks of voluntary wheel exercise significantly increased GAD67 mRNA expression in the dentate gyrus (DG) and CA1 subfields of the hippocampus, with a trend for increased expression in the CA3 subfield. Because brain‐derived neurotrophic factor (BDNF) is widely recognized for its upregulation in response to exercise, we measured BDNF expression as a positive control. Consistent with previous observations, running enhanced BDNF expression, specifically in the DG subfield of the hippocampus. Runners also consumed less food and water, and gained less weight, over the course of the experiment. In rodents, reductions in ingestive behavior and attenuated weight gain are typically observed following repeated psychological stress, which compromises hippocampal inhibitory tone and reduces BDNF expression. Therefore, the presence of enhanced GAD67 and BDNF expression in the context of physiological indicators of stress presents an intriguing paradox that may account for the changes in sensitivity to stress observed following running wheel activity. Grant Funding Source : P01AG009973‐18