Changes of salivary functions in experimental periodontitis model rats

Objective This study was designed to investigate the mechanism of salivary dysfunction in an experimental periodontitis rat model and to examine the improvements in salivary secretion following treatment of the experimental periodontitis. Methods In the experimental periodontitis rat model, which included a unilateral ligature for 4 weeks around the second upper molar, several salivary functions were investigated. Changes in the salivary function were evaluated 4 weeks after removal of the ligature in some rats. Results The periodontitis model showed significant reductions in the weight of the bilateral major salivary glands and pilocarpine-induced salivary secretion. The model also showed an increase in the number of apoptotic cells in bilateral salivary glands. According to Ca²⁺ imaging and Western blotting, there were no differences in the muscarine-induced intracellular Ca²⁺ mobilization in acinar cells or in the M3 receptor and AQP5 expression levels in the salivary glands between the sham and the periodontitis model. Following removal of the ligature, differences in the weights of salivary glands and pilocarpine-induced salivary secretion between the sham and the periodontitis model animals were not found. Conclusion These results suggest that experimental periodontitis leads to hyposalivation and that relief from it improves salivary function. It is likely that lower levels of salivary secretion are caused by the decrease of functional acinar cells in salivary glands in the experimental periodontitis model, and the bilateral gland effects in the unilateral periodontitis model are caused by systemic rather than by local effects.