Effect of sympathetic nervous activity on alveolar bone loss induced by occlusal hypofunction in rats

Abstract Objective To elucidate the effect of sympathetic nervous activity on alveolar bone loss induced by occlusal hypofunction in rat molars. Design Occlusal hypofunction in the molar area was produced by attaching appliances to rat maxillary and mandibular incisors. In addition, a non-selective β-adrenergic receptor antagonist, propranolol, was administered orally to rats in drinking water to pharmacologically suppress sympathetic nervous activity. After 1 week, alveolar bones in all groups were examined by micro-CT, histomorphometry and histology to determine their trabecular bone phenotypes and histological changes. Results The marrow spaces of the interradicular alveolar bone of rat mandibular first molars (M1) increased in the occlusal hypofunction group (Group H) but not in the control group (Group C), whilst these decreased in rats in the occlusal hypofunction group that were administered propranolol (Group HB). Bone volume/tissue volume (BV/TV), trabecular thickness (Tb.Th) and trabecular number (Tb.N) for interradicular alveolar bone in M1 in Group H were significantly lower than those in Group C, whereas those in Group HB remained as high as those in Group C. The number of TRAP-positive cells in Group H increased compared to that in Group C, whereas it significantly decreased in Group HB. Conclusions These results suggest that sympathetic nervous activity may influence the alveolar bone loss induced by occlusal hypofunction.