Nociceptive behavior of Female Rats using Piperine in the region of Temporomandibular Joint in the presence of local chronic inflammation and stress

Abstract

The Temporomandibular Dysfunction (TMD) is a condition that may affect the masticatory muscles, temporomandibular joint (TMJ), and related structures. The most common signs and symptoms are joint sounds and muscle and / or joint pain. TMD has high prevalence in adult populations, affecting more women. Conditions of pre-existing pain, sex hormones, psychological factors and depression seem to contribute to the progression and exacerbation of painful symptoms. In order to understand some of the mechanisms involved in this pathology, animal experiments were developed using substances that would cause painful symptoms in the TMJ. But all these studies were done in male animals. Due to the higher prevalence in females and the possibility of hormonal influences on pain perception, this research aims to develop a model of nociceptive behavior in the TMJ region of female rats. Different concentrations of Piperine solution will be used, to evaluate possible changes in that behavior in the course of time, under TMJ chronic inflammation, and with or without condition of chronic stress. This research may help in conducting the clinical diagnosis and therapeutic management of patients with TMD, and in understanding the possible changes of nociception perception when there is chronic inflammation associated with stress. A randomized double-blind experimental study will be performed, using 192 female Wistar rats that will be divided into four groups: Group I (control): healthy animals without TMJ inflammation and without chronic stress; Group II: animals under chronic inflammation in the right TMJ and without chronic stress; Group III: animals without TMJ inflammation, but under chronic stress; and Group IV: animals under chronic stress and chronic joint inflammation. All groups will be subdivided into six sub-groups, which will be injected into the right TMJ: solution of 80% sterile saline, 10% Tween 80 and 10% ethyl alcohol; and solutions of 1, 2, 3, 4 and 5¼g of piperine diluted in 80% sterile saline, 10% Tween 80 and 10% ethyl alcohol. The data with homogeneity of variance will be compared by analysis of variance (ANOVA) where the post-hoc multiple comparisons will be performed by the Bonferroni test. The correlation between the different concentrations of piperine, inflammation and stress will be tested by Spearman coefficient. The probability level of less than 0.05 is considered statistically significant.