Dopaminergic modulation of reward discounting: a systematic review and meta-analysis

Although numerous studies have suggested that pharmacological alteration of the dopamine (DA) system modulates reward discounting, these studies have produced inconsistent findings. Here, we conducted a systematic review and meta-analysis to evaluate DA drug-mediated effects on reward discounting in studies of healthy rodents. This produced a total of 1,343 articles to screen for inclusion/exclusion. From the literature, we identified 117 effects from approximately 1,549 individual rodents. Using random-effects with maximum-likelihood estimation, we meta-analyzed placebo-controlled drug effects for (1) DA transporters, (2) DA D1-like receptor agonists and (3) antagonists, and (4) D2-like agonists and (5) antagonists. Meta-analytic effects showed that DAT-binding drugs decreased reward discounting. While D1 and D2 antagonists both increased discounting, agonist drugs for those receptors had no significant effect on discounting behavior. These findings suggest a nuanced relationship between DA and discounting behavior and urge caution when drawing generalizations about the effects of pharmacologically manipulating dopamine on reward-based decision making.