Expression of substance P in rat periodontal alveolar bone after denervation

The aim of this study is to investigate substance P (SP) expression in rat periodontal alveolar bone after inferior alveolar nerve transection. 60 male Wistar rats were divided into six groups randomly. Mandibular alveolar bones were removed from the denervated rats according to sacrifice time points (0, 3, 7, 14, 21, and 28 days after operation). Immunohistochemical staining was applied to trace the expression of SP. The mRNA and protein levels of SP in periodontal alveolar bone were quantified by real-time PCR and Western blot techniques. Positive expressions of SP were located in sensory nerve fibres and blood vessels that distributed in periodontal ligaments and alveolar bone. SP-immunopositive expressions changed at different time points as a result of denervation. Expressions of SP decreased in periodontal alveolar bone at day 3, and the lowest expression level was measured at day 7 after operation. In the late stages of the study, SP expressions increased since 14 days and then gradually got back to normal levels at 28 days. To conclude, inferior alveolar nerve transection leads to the down-regulation of SP mRNA and protein in alveolar bone. SP may also play an important role in the compensation or recovery of innervation.