UVM Theses and Dissertations
Format:
Print
Author:
Eddy, Meghan C.
Dept./Program:
Psychology
Year:
2013
Degree:
M.A.
Abstract:
Research on voluntary physical exercise has revealed many benefits, aside from its obvious roles in improving and maintaining health. While much of the previous work examining health h benefits gained from exercise in humans has focused on maintenance or recovery of function in the aging or impaired brain, the rodent literature has tended toward effects specifically on the hippocampus and hippocampus-related behaviors. Here, male rats had two weeks access to a locked (non-exercise controls) or unlocked (exercise treatment) running wheels and were tested on a measure of cognitive flexibility, set-shifting. This task is not reliant on the hippocampus, but rather connections between the dorsomedial (DMS) (set 2) and dorolateral (DLS (set 1) striatum and the medial prefrontal cortex (mPFC). Exercising rats performed better at the initial discrimination (set 1) portion of the task. Striatum tissue from these rats was analyzed for dopamine transporter (DAT) expression. It was found that there was an exercise-related decrease in DAT expression.
Follow-up experiments focusing on the role of D1 and D2 receptors in the DLS revealed that infusion of a D1 antagonist (SCH23390) into the DLS prior to testing enabled non-exercising rats to perform at comparable levels to exercisers, with no discernable effect on the performance of the exercisers. Conversely, when eticlopride, a D2 antagonist was infused, there was no effect on non-exercisers, but the performance of exercisers was reduced to that of nonexercising controls. These results suggest that exercise affects the striatal dopamine system. Particularly, DAT is being down-regulated, perhaps resulting in more synaptic dopamine, and a more efficiently operating system. Also, D1 receptors appear to be down-regulated in exercisers, whereas D2 receptors are up-regulated. These results add to the literature showing specific brain adaptations in response to voluntary exercise, and importantly provide evidence of changes outside of the hippocampus.
Follow-up experiments focusing on the role of D1 and D2 receptors in the DLS revealed that infusion of a D1 antagonist (SCH23390) into the DLS prior to testing enabled non-exercising rats to perform at comparable levels to exercisers, with no discernable effect on the performance of the exercisers. Conversely, when eticlopride, a D2 antagonist was infused, there was no effect on non-exercisers, but the performance of exercisers was reduced to that of nonexercising controls. These results suggest that exercise affects the striatal dopamine system. Particularly, DAT is being down-regulated, perhaps resulting in more synaptic dopamine, and a more efficiently operating system. Also, D1 receptors appear to be down-regulated in exercisers, whereas D2 receptors are up-regulated. These results add to the literature showing specific brain adaptations in response to voluntary exercise, and importantly provide evidence of changes outside of the hippocampus.