Increased duration of dopamine receptor antagonist-induced effects on both behaviour and striatal dopamine turnover...

The present results show that the effects on striatal dopamine (DA) turnover of a single dose of the DA receptor antagonists haloperidol or raclopride in the rat, are dependent on the activity level of the animal during treatment. Thus, animals tested for treadmill locomotion 30 and 60 min. after injection display an increased striatal DA turnover at 90 or 120 min. (raclopride and haloperidol, respectively) compared with control animals which were administered the same dose of the DA antagonist, but which did not have the treadmill tests. The relevance of these findings with respect to individual differences in clinical response and occurrence of side effects as well as the reported difficulties in obtaining good correlations between plasma levels and clinical response with DA-receptor blocking antipsychotic drugs are discussed.