Methylphenidate reduces rats’ temporal discounting of aversive outcomes

Understanding the impact of delayed consequences on decision-making is a scientific goal with important clinical implications. Previous research suggests that dopamine-agonist administration decreases sensitivity to the delay of positive events, but its impact on sensitivity to the delay of aversive events has been scarcely studied. The present study aimed to evaluate the effect of acute administration of methylphenidate (MPH) on rats’ temporal discounting of aversive consequences. Sixteen Wistar rats were trained in a choice task that presented a choice between (a) an immediate small reward without punishment and (b) an immediate large reward accompanied by an electric shock delayed by 0, 4, 8, 12, or 16 s. These delays were presented within a session in ascending order for half of the subjects and in descending order for the remaining subjects. When preference was stable, different doses of MPH (4, 8, and 16 mg/kg) were administered. For both groups of rats, MPH reduced preference for the alternative associated with shock in a dose-dependent way. Additionally, results from a control condition in which shock was presented immediately indicated that MPH did not increase sensitivity to the shock. Taken together, these findings suggest that MPH reduces temporal discounting of aversive consequences and highlights the involvement of the dopaminergic system in decision-making involving delayed aversive consequences. Further research is needed to better understand the specific pharmacological mechanisms underlying these results.