Danitracen lowered serotonin levels in the cerebrum, cerebellum, medulla and the whole brain. The drug did not appear to affect the concentration of 5-HIAA except in the cerebellum where there was a considerable depletion. Danitracen pretreatment led to a lowering in the 5-HT levels in the various parts of the brain without influencing 5-HIAA levels in the whole brain and decreased NE levels in apomorphine and amphetamine-treated rats. The findings indicate that the mechanism of action of danitracen also involves noradrenergic neurons along with a possible increase in the metabolism of 5-HT.