Different effects of haloperidol and extinction on instrumental behaviours

The effects of 0.1 mg/kg haloperidol (HP) and extinction following FR20 training in rats were compared. Animals under extinction responded at higher rates at the beginning of the session than rats treated with HP, but slower than HP-treated animals at the end of the session. Extinction subjects also emitted proportionately more ratios that were faster than the previous baseline response rate when compared to HP subjects. In a second experiment, animals were reinforced under an FI30-s schedule for merely being on one floor panel of a chamber which also measured locomotor activity. Comparison of the effects of 0.4 mg/kg HP and extinction revealed that both manipulations reduced locomotor activity, while only extinction reduced time on the reinforced panel. The results of these experiments were viewed as contrary to the hypothesis that dopamine antagonist drugs reduce the primary reinforcing impact of food. However, they were seen as consistent with the notion that HP reduced incentive-related motor activity.