Neurogenic component in ligature‐induced periodontitis in the rat

Abstract. Effect of ligation on the vascular permeability in the gingiva and alveolar mucosa encircling the mandibular left 1st molar was studied in rats with and without capsaicin pretreatment. Vascular permeability was assessed by the Evans blue extravasation. Ligation caused a significant augmentation in vascular permeability of the gingivomucosal tissue at day 8 (right: 18.14±1.68 μg g−1; left (ligature): 38.21 ±2.43 μg g−1, n=8, p(0.001) and at day 14 (right: 20.31 ±1.71 μg g−1: left (ligature): 36.98±2.73 μg−1, n= 8, p(0.001). 4 days after ligation, no difference could be observed in vascular permeability in the oral mucosa of the ligated side (left: 23.14±1.21 μg−1) as compared to the side without ligature (right: 23.5±1.45μg g−1, n=8, NS). There was no elevation of vascular permeability of gingivomuscosal tissue around the ligation in rats pretreated with capsaicin either in newborn age (right: 23.92±1.76 μg g−1; left (ligature): 23.51±2.16 μg g−1, n=8, NS) or in adult age (right: 20.61±1.62 μg g−1; left (ligature): 20.85±1.07 μg g−1, n=8, NS). Light microscopical studies of oral mucosa revealed, that 8 and 14 days after the ligature placed around the mandibular left 1st molar of the rat, there resulted an accumulation of inflammatory cells in the connective tissue. There was no inflammatory reaction in the gingivomucosal tissue of the side of the ligature 4 days after ligature, neither could inflammatory reaction be detected 14 days following ligation in the oral mucosa of rats systemically pretreated with capsaicin either neonatally or in the adult. Based on these observations, it can be assumed that neurogenic mechanism plays a crucial role in the development of inflammation in the oral cavity induced by mechanical and/or bacterial stimulation frequently found in clinical practice.