Immunohistological Changes Observed Over Time in Neuronal-Intermediate-Filament-Protein after Neonatal Desensitisation

Objectives: The neonatal application of capsaicin produces a selective loss of nociceptive fibres in the dental pulp, resulting in many changes in the dentin-pulp-complex. The purpose of this study was to determine if age has an influence on the reduction or elimination of intermediate-nerve-filament in the neonatal capsaicin-treated rat over time. Methods: 48 wistar rats served as the experimental group where capsaicin (50mg/Kg body weight) in a sterile vehicle was systemically administered on the 3rd postnatal day. 48 control animals were injected with the sterile vehicle on the same day. Groups (n=12) of experimental and control animals were sacrificed via deep anaesthesia, cardial intravital-perfusion and fixation at 30 days, 60 days, 90 days and 155 days of life. Jaws were dissected and immunohistology was performed on frozen cryosections of left lower jaws with primary antibody against Peripherin (PER) in order to localize intermediate-nerve-filament within the dental pulp of each specimen. Micrographs were produced from the distal pulp-horn of the first molar at magnifications of 10X and 25X, where Scion image was applied. Here the pixel numbers per inch2 of positive immunohistological staining was measured. SPSS was used to calculate Student t-test in order to analyse differences between experimental and control groups within each age category. Results: Our results demonstrate significant differences between the experimental and control groups at 60, 90 and 155 days but not at 30 days. Conclusion: From our results we may conclude that globular neuronal proteins of neuronal intermediate-filament presenting within neuronal structures in the pulp tissue are changed with age in capsaicin-treated rats compared to control animals. Acknowledgements: This study was supported by the Heinrich-Heine-University Research-Commission and the German-Dental-Association (DGZMK).