Early life stress exacerbates bone resorption and inhibits anxiety-like behaviour induced by apical periodontitis in rats

Abstract

Aim: To evaluate the influence of the early life stress (ELS) on the severity of the apical periodontitis (AP) in Wistar rats. Methodology: Forty male Wistar rats were divided into four groups (n = 10): Control rats; AP—rats with AP; ELS—rats subject to ELS; AP + ELS—rats exposed to ELS and subject to AP. ELS was induced by maternal separation (MS) for a period of 3 h for 21 consecutive days. AP was induced via pulp exposure of the first and second right maxillary molars to the oral environment for 40 days. Three days before euthanasia, all rats underwent behavioural analysis to measure anxiety levels by elevated zero maze. Then, the rats were euthanized and the maxillas were removed to assess the occurrence and severity of AP. The periapical region was evaluated for the intensity of the inflammatory infiltrate and the extent of bone loss. The Mann–Whitney test was performed for nonparametric data, and the Tukey's or Student's t-test was performed for parametric data (p <.05). Results: The intensity of the inflammatory infiltrate was significantly larger in the AP + ELS group when compared with AP group (p <.05). The AP + ELS group exhibited significantly greater alveolar bone loss, with a periapical lesion size of 103.5 ± 29.88, compared with 72.3 ± 22.28 in the AP group (p <.05). Rats with AP displayed higher anxiety-like behaviour in relation to the control group (p <.05). However, exposure to ELS abolished the AP-induced increased anxiety-like ‘behaviour’ throughout, since that rats from AP + ELS group attended more the open arms than non-stressed rats with AP (p <.05). Conclusion: Early life stress is predictive of the severity of AP exacerbating the inflammatory process and increasing periapical bone resorption.