Methods: Male 9-mo-old SAMP8 were used in this study. The bite-raised condition was induced by increasing the vertical dimension of the bite by applying resin to the upper molars (approximately 0.1 mm). In situ hybridization and ELISA were used to evaluate BDNF protein and mRNA levels, respectively, and the TUNEL method was used to measure apoptotic cells.
Results: BDNF protein and mRNA levels were significantly lower in the hippocampus of bite-raised mice compared with controls. The number of TUNEL-positive cells in the hippocampal dentate gyrus was significantly higher in the bite-raised mice than in controls.
Conclusions: BDNF is essential for all levels of cell generation, including cell proliferation, survival, and differentiation of newborn cells. Our results suggest that the bite-raised condition affects neurotrophic factor and apoptosis. Therefore, decreased BDNF expression might contribute to the impaired neurogenesis and apoptosis induced by raising the bite.