[Effect of idebenone (CV-2619) on brightness discrimination learning in rats with central serotonergic dysfunction]

The effect of 6-(10-hydroxydecyl)-2, 3-dimethoxy-5-methyl-1, 4-benzoquinone (idebenone, CV-2619) on brightness discrimination learning of the operant type was examined in rats with central serotonergic dysfunction. The animal model was produced by feeding Wistar rats a diet deficient in tryptophan (a precursor of serotonin) as the control group. The control rats with central serotonergic dysfunction showed lower ability to learn the discrimination task (multiple VI 15 seconds extinction schedule) than normal feeding rats. Rats which were chronically administered with idebenone (60 mg/kg/day) admixed with the tryptophan deficient diet were used as an experimental group. In the control and experimental groups, total responses (R+ + R-) were significantly increased in the early stage of learning test period, compared with the normal rats. In the late stage of the learning periods, the numbers of R-decreased in idebenone-treated group but not in control group. Therefore, the correct response ratio [( R+/(R+ + R-)] X 100) was significantly higher in the treated group than in the control. The results suggest that idebenone, which has an improving action on cerebral energy metabolism and a stimulating action on central serotonergic turnover, may exert an ameliorating effect on impaired discrimination learning in rats with central serotonergic dysfunction.