Antagonism by haloperidol of the L-DOPA-induced disruption of a successive discrimination in the rat.

Male rats were trained to perform a conditioned avoidance response combined with a successive discrimination in a shuttle-box. The administration of L-DOPA, 100 mg/kg i.p., after inhibition of peripheral dopa decarboxylase, disrupts the discrimination but not the acoidance behaviour, whereas the administration of the antipsychotic agent haloperidol (HPD), 0.125 mg/kg i.p., disrupts the avoidance behaviour but not the discrimination. The L-DOPA-induced disruption of the successive discrimination was completely antagonized by 0.25 mg/kg of HPD. The present data show that administration of the antipsychotic agent HPD not only inhibits behaviour but also can improve the behaviour in animals with a disturbed function.