The basic study for the maintenance of oral health in an aging society

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This project was to clarify the role of the nigrostriatal dopaminergic pathway in the sequential progress during mastication.Some clinical observations and animal experiments have been suggested that the deficencyt of the oral function decrease the activities of brain function inclulding learning and memory. However; the detail of this mechanisrn has not been clarified. In order to understand the relationship between brain and the oral function, we focused on the bioactive materials in brain, in this project.We obtained the findings in this study as follows ;1) To know the relationship between the monoamine and the activity trigeminal motor function properties of the hyperpolarizing spike afterpotential and the low-voltage activated Ca^<2+> channel were examined in vitro. It was found serotonine increased the excitability of the trigeminal motoneurons.2) By using the microdialysis method, the dopamine concectration in the putamen was found to increase significantly during mastication c … More ompared with resting period. And the bilateral 6-hydroxydopamine lesions of the nigrostriatal dopaminergic pathway induced the change of the movement pattern during intake behavior. These results suggested that the nigrostriatal dopaminergic pathway might play a role in the sequential progress during the mastication.3) When the experimental animals were induced chronic pain by making the inflammation in the temporomandibular joint or parotid gland, activities of neurons ln the spinal trigeminal nucleus caudaris were recorded. The data indicated the peripheral and central sensitization occurred, and suggested the opioid might be involved in this sensitization.4) Using the experimental animals in which masticatory behavior were restricted by giving them only soft food, c-fos expression, in the dorsal horn were examined when inflammation weas induced in hindpaw. C-fos expression was decreased when that experimental animal were activated the masticatory function with hard food and wood stick. These results suggested the possibility that is enhancement of mastication evoked the secretion of the opioid. Less