Differential susceptibility to periodontitis in genetically selected Wistar rat lines that differ in their behavioral and endocrinological response to stressors

This study tests the model presented previously by Breivik er nl. (1996), i n which the extent of periodontitis, an inflammatory disease, is predicted from the reactivity of the HPA-axis. Briefly, the model implies that elevat ed plasma levels of corticosterone modulate the immune system by shifting t he T-helper balance toward a more Th2 response, which, alternately, increas es the sensitivity to periodontitis. To test this model, two genetically di stinct types of rats that differ both behaviorally and endocrinologically i n their response to stress thigh corticosterone responding APO-SUS rats and low corticosterone responding APO-UNSUS rats) were compared. Periodontitis was experimentally induced through the placement of a ligature and measure d as the extent of tissue (fiber and bone) loss, both histologically and ra diographically. The results show that, as expected, APO-SUS animals are mor e sensitive to periodontitis, i.e., show more fiber and bone loss, than APO -UNSUS animals. These data are in agreement with findings in Fischer and Le wis rats, as well as with corticosterone treated and adrenalectomized anima ls and suggest that genetic factors underlying the variation in the reactiv ity of the HPA-axis (and, accordingly, their behavioral response to stress) play an important a role in the development of inflammatory diseases.