マウス咀嚼筋における筋疲労，浮腫性変化および痛みの関連に関する研究

抄録

Objective: To clarify the relationship between edematous changes and pain in the masseter muscle, we investigated whether plasma extravasation might be induced in the mouse masseter muscle when muscle fatigue with gnawing behavior occurred.
Study design: When a mouse is restrained in a narrow cylinder with blocking at the front end with a thin plastic strip, it gnaws away at the strip to escape. The mice in the experimental group were restrained in such a cylinder for two hours. In a control group, the mice, whose tails were fixed to the cylinder using tape, could not reach the strip and thus could not bite it. Using these models, we examined plasma extravasation by the Evans blue (EB) dye method. Furthermore, to investigate the relationship between masseter muscle pain and plasma extravasation, local anesthesic was injected into the right masseter muscle, with the control side injected with saline alone.
Results: The level of EB dye in the masseter muscle of the experimental group was higher than that of the control group. There was a high correlative relationship between the weight reduction of the plastic strip and the EB dye. The level of EB dye at the anesthetized side was significantly decreased compared with that at the saline-injected side.
Conclusion: This result suggests that the masseter muscle pain induced by muscle fatigue evokes plasma extravasation, resulting in edematous changes in the masseter muscle.