The effect of amperozide on DA synapses was studied in 6-OHDA lesioned rats exhibiting a specific turning behaviour in response to the DA agonists apomorphine and pergolide or indirectly acting stimulating agents like amphetamine. Amperozide, unlike classical neuroleptics, failed to antagonize apomorphine induced turning behaviour in a regular fashion, but showed pergolide antagonism within the D2 receptor selective dose range, suggesting a type of selective interference with dopaminergic nerve transmission which differs from that caused by classical neuroleptics. Furthermore, amperozide antagonized the turning behaviour induced by amphetamine, presumably by interfering with the availability of newly synthesized DA and NA suggesting a similar influence also on other DA releasing agents. Although amperozide potentiated the effects of alpha-MPT, the drug seemed not to influence the reserpine sensitive pool of DA.