Effects of Vitamin D and Memantine on Repetitive Mild Traumatic Brain Injury via mTOR, TRPM2, and GABA Expression Levels on Juvenile Rats.

Aim: To investigate the effects of vitamin D and memantine on the healing process in juvenile rats with repetitive brain injury (rTBI) and to elucidate the mechanisms underlying these potential therapeutic effects.

Material and methods: Juvenile rats were randomly allocated into seven groups, with eight rats per group: sham-operated (Group I), trauma (Group II), memantine supplementation (10 mg/kg) pre-trauma (Group III), vitamin D supplementation (5 µg/kg) pre-trauma (Group IV), vitamin D supplementation post-trauma (Group V), memantine and vitamin D supplementation post-trauma (Group VI), and vitamin D supplementation pre- and post-trauma with post-trauma memantine supplementation (Group VII). A modified repeated weight drop model was employed to induce rTBI. Brain tissues and blood samples were collected for analysis. Expressions of the mammalian target of rapamycin (mTOR), temporary receptor potential (TRPM2), and GABA receptors were assessed via immunohistochemistry. Levels of 8-hydroxy-2-deoxyguanine (8-OHdG) were determined using high-performance liquid chromatography (HPLC). Matrix metalloproteinases -2 and -9, tissue inhibitors of metalloproteinases-1 and-2, and NADPH oxidation-4 levels were determined using commercially available enzyme-linked immunosorbent Test kits. Immunohistochemistry analyses were performed on the brain cortex and hippocampus.

Results: The levels of 8OHdG/106dG, MMP-2, MMP-9, TIMP-1, -TIMP2, and NOX-4 were significantly higher in the trauma group than in the other groups. No difference was found between the control and Pre Vit D+Mem+Post Vit D groups regarding 8OHdG/106dG, MMP-2, -9 and NOX-4 levels. Normalized expressions of mTOR and TRPM2 were observed in Groups VI and VII. Conversely, GABA expression levels decreased in Group II, with the most pronounced therapeutic effects observed in Group VII.

Conclusion: Memantine and vitamin D positively affected rTBI when used alone. Their combined use exhibited greater therapeutic outcomes. These effects are mediated by mTOR mRNA, TRPM2 mRNA, and GABA mRNA expressions.