Dopaminergic modulation of reward discounting in healthy rats: a systematic review and meta-analysis
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ORIGINAL INVESTIGATION
Dopaminergic modulation of reward discounting in healthy rats: a systematic review and meta-analysis Jaime J. Castrellon 1,2
&
James Meade 2,3 & Lucy Greenwald 2,4 & Katlyn Hurst 2,4 & Gregory R. Samanez-Larkin 1,2
Received: 2 September 2020 / Accepted: 13 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Rationale Although numerous studies have suggested that pharmacological alteration of the dopamine (DA) system modulates reward discounting, these studies have produced inconsistent findings. Objectives Here, we conducted a systematic review and pre-registered meta-analysis to evaluate DA drug-mediated effects on reward discounting of time, probability, and effort costs in studies of healthy rats. This produced a total of 1343 articles to screen for inclusion/exclusion. From the literature, we identified 117 effects from approximately 1549 individual rats. Methods Using random effects with maximum-likelihood estimation, we meta-analyzed placebo-controlled drug effects for (1) DA D1-like receptor agonists and (2) antagonists, (3) D2-like agonists and (4) antagonists, and (5) DA transporter-modulating drugs. Results Meta-analytic effects showed that DAT-modulating drugs decreased reward discounting. While D1-like and D2-like antagonists both increased discounting, agonist drugs for those receptors had no significant effect on discounting behavior. A number of these effects appear contingent on study design features like cost type, rat strain, and microinfusion location. Conclusions 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. Keywords Dopamine . Pharmacology . Discounting . Delay . Probability . Effort . Decision-making . Meta-analysis
Introduction Every day, all animals make decisions that involve weighing costs and benefits. Animals regularly devalue rewards that are relatively delayed, uncertain, or require more effort than sooner, more certain, or less effortful ones. This process is known as reward discounting. For example, people often choose to eat at restaurants because it is less effortful or time-consuming
Some of the results reported in this manuscript were presented at the Annual Meeting of the Society of Biological Psychiatry (2019). * Jaime J. Castrellon [email protected] 1
Department of Psychology & Neuroscience, Duke University, Durham, NC, USA
2
Center for Cognitive Neuroscience, Duke University, Box 90999, Durham, NC 27708, USA
3
Department of Chemistry, Duke University, Durham, NC, USA
4
Department of Biology, Duke University, Durham, NC, USA
than cooking a meal. In this scenario, people place a greater value on food that is immediately available or easy to acquire. While most individuals discount to some degree, a range of factors influence whether one discounts rewards more steeply (stronger devaluation) or not at all. In humans, for example,
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