Abstract: DL-Tetrahydropalmatine (THP) is an active principle found in the Chinese herb Corydalis ambigua. It possesses sedative and analgesic activities. THP had been reported to deplete dopamine (DA), noradrenaline (NA) and serotonin in rat brain. The effect of reserpine in reducing the transmitters and its sedative action could be reversed by MAOI i. e. reserpine-reversal. In order to investigate the influence of pargyline on THP induced depletion of catecholamines, NA, DA and their metabolites were measured by high performance liquid chromatography coupled with electrochemical detection. It was shown that the decrease of NA and DA concentrations in the limbic area was reversed by pretreatment with pargyline, whereas that in the striatal area returned to normal. From this study further evidence was obtained to support the hypothesis that THP is a monoamine depletor with reserpine-like action.