Spontaneous Bruxism Activity Attenuates Stress Effect in Stressed Rats

Objectives: Stress involves a serial of dynamic reactions that might interfere with the normal functioning of the living body, which in response to that has the ability to achieve stability through change (allostasis) by activation of protective mechanisms taking place in the nervous system, endocrine system and the immune system. Previous research has suggested that bruxism like activity (BLA) has a capacity to alleviate stress effects as an allostatic function. The purpose of this study was to investigate the relation between BLA and physiological markers, and between BLA and damage to internal organs (gastric mucous) using the rat restraint model of stress ulceration.

Methods: Male Wister rats aged eight weeks (n=35) were divided into two groups: control (n=15) and experimental (n=20). When restraint stress was applied to the experimental group, the muscle activity of BLA was recorded and blood samples were taken after 6 hours. Levels of catecholamine, cortisol, corticosterone and neutrophil/lymphocyte ratio were measured. Additionally, the stomach was removed and the damage level of the mucous membrane was evaluated.

Results: Experimental group showed significant increase in the physiological parameters measured compared with the control group. Furthermore, there was a significant negative correlation between these parameters and the BLA time. Also, significant correlations were found between catecholamine and neutrophil and between cortisol and lymphocyte. The proportion of neutrophil to lymphocytes in blood leukocytes inversed at the end of restraint stress and was sustained until the end of the trial.

Conclusions: These results indicate that activity of the masticatory organ plays an important allostatic role in mitigating effects produced by stress.

This work was supported by an Open Research Center subsidy (H18) from MEXT.