Inhibitory effect of the root ofCoptis japonica on catecholamine biosynthesis in PC12 cells

The effect of the root ofCoptis japonica (COPT), both the dichloromethane soluble (CH₂Cl₂) and insoluble (H₂O) fractions, on catecholamine contents and tyrosine hydroxylase (TH) activity in PC12 cells was investigated. CH₂Cl₂ and H₂O fractions showed 21 and 53% inhibitions on dopamine content, respectively, at a concentration of 40 μg/ml in medium: the H₂O fraction provided a greater inhibitory effect. The TH activity was reduced by the treatment of COPT (H₂O fraction). These results suggest that COPT has an inhibitory effect on the catecholamine biosynthesis by the reduction of TH activity in PC12 cells.