The biochemical effects of minaprine, a new psychotropic drug, were investigated on striatal dopaminergic neurons in the rat. Minaprine did not displace [3H]spiperone in-vitro binding from striatal membranes but had clear effects on dopamine (DA) metabolites. Homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) were significantly decreased in a dose-dependent manner after intraperitoneal administration of minaprine 30 min before killing. In rats injected with minaprine 15 mg kg-1 i.p. at different intervals, the decrease in striatal HVA and DOPAC was time-dependent and a concomitant rise in 3-methoxytyramine (3-MT) concentrations was observed. The maximum of these effects was reached 30 min after minaprine. When administered 5 min after a monoamineoxidase (MAO) inhibitor (pargyline, 100 mg kg-1 i.p.) and 30 min before killing, minaprine did not affect pargyline-induced changes in HVA, DOPAC and 3-MT levels. This together with other data suggests that minaprine affects DA metabolism by acting, at least partially, at presynaptic level through in-vivo inhibition of MAO activity.