Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Hylin, Michael


Traumatic brain injury (TBI) is one of the leading causes of death and disability in children. The effects of TBI are not limited to the brain but also impacts the gut. Within the gut are residential microbes that can mediate brain physiology and resulting behavior. Chronic administration of the probiotic Lactobacillus reuteri (L. reuteri) provides neuroprotection and improves long-term behavioral outcomes after TBI. The primary goal of this study was to address how L. reuteri affects neurodegeneration and inflammation in the 7-day period after TBI. The secondary goal was to establish if short-term treatments with L. reuteri improved behavioral outcomes after TBI. For this series of studies, animals received a bilateral craniotomy with a single cortical contusion injury over the right parietal lobe. Following injury, animals were given daily doses of the probiotic L. reuteri or a broth vehicle control for up to 7 days. Animals were sacrificed at days 1, 3, 5, 7, and 30 following injury. These times represent the acute (1-7 days) and chronic (35 days) period after injury. The results of this study show that while injured animals demonstrated inflammation, neurodegeneration, and decreased cortical volume, L. reuteri treated animals had significantly attenuated changes compared to broth counterparts at days 1, 3, 5, and 7. By day 35, inflammation was not different between treatments but L. reuteri animals showed less cortical loss compared to broth treated animals. With respect to behavior, acute treatment of L. reuteri did not show improvements over broth treated animals. Taken together, it was observed that administration of the probiotic L. reuteri rapidly and robustly reduced pathophysiology after juvenile TBI (jTBI), however these effects did not translate into behavioral improvements. Thus, further studies are needed to examine whether animals need to be undergoing treatment at the time of testing in order to receive behavioral benefit.




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