Biochemical studies of dopaminergic activation by stimuli of corn oil in the oral cavity in mice.

We investigated the effects of corn oil stimuli in the oral cavity on monoaminergic neurones by measuring the amount of monoamines and their metabolites in brains of mice. Intraoral injection of corn oil (0.1 ml) increased dopamine (DA) turnover rate in the cortex 3, 5 and 10 min after injection in mice. A significant increase of DA turnover rate was also observed in midbrain 10 min after the corn oil injection. Turnover rates of noradrenaline (NA) and serotonin (5-HT) were not affected by the corn oil injection in any of the regions or times tested. In the chronic study, DA and 5-HT contents in the left and right cortexes and 5-HT contents in diencephalon in the chronic corn oil-fed group were significantly higher than those in the-control but NA contents were not significantly different between the two groups in all regions. In conclusion, the present results suggested that the stimuli of corn oil in the oral cavity might activate dopaminergic systems in the brain of mice and its chronic stimuli might increase DA contents in the brain. Although 5-HT contents increased in the brains of mice by the chronic corn oil intake, its physiological implication remains to be elucidated.