Pharmacological studies of effort-related decision making using mouse touchscreen procedures: effects of dopamine antagonism do not resemble reinforcer devaluation by removal of food restriction

• Published in: Psychopharmacology Vol. 237; no. 1; pp. 33 - 43
• Main Authors: Yang, Jen-Hau, Presby, Rose E., Jarvie, Adam A., Rotolo, Renee A., Fitch, R. Holly, Correa, Mercè, Salamone, John D.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2020; Springer; Springer Nature B.V
• Subjects: Analysis; Animals; Biomedical and Life Sciences; Biomedicine; Carbohydrates; Choice Behavior - drug effects; Decision making; Decision Making - drug effects; Dopamine; Dopamine - pharmacology; Dopamine Antagonists - pharmacology; Dopamine D2 receptors; Feeding Behavior - drug effects; Food; Food availability; Food intake; Food preferences; Haloperidol; Haloperidol - pharmacology; Interactive computer systems; Male; Mesolimbic system; Mice; Motivation; Neurosciences; Operant conditioning; Original Investigation; Pellets; Pharmacology/Toxicology; Phenols; Psychiatry; Reinforcement; Strawberries; Panel pressing; Schizophrenia; Dopamine; Motivation; Preference test; Bussey-Saksida chambers
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-019-05343-8

Rationale
Effort-based decision-making tasks offer animals choices between preferred reinforcers that require high effort to obtain vs. low effort/low reward options. The neural mechanisms of effort-based choice are widely studied in rats, and evidence indicates that mesolimbic dopamine (DA) and related neural systems play a key role. Fewer studies of effort-based choice have been performed in mice.
Objectives
The present studies used touchscreen operant procedures (Bussey-Saksida boxes) to assess effort-based choice in mice.
Methods
CD1 mice were assessed on a concurrent fixed ratio 1 panel pressing/choice procedure. Mice were allowed to choose between rearing to press an elevated panel on the touchscreen for a preferred food (strawberry milkshake) vs. consuming a concurrently available less preferred alternative (high carbohydrate pellets).
Results
The DA D
2
antagonist haloperidol (0.05–0.15 mg/kg IP) produced a dose-related decrease in panel pressing. Intake of food pellets was not reduced by haloperidol, and in fact, there was a significant quadratic trend, indicating a tendency for pellet intake to increase at low/moderate doses. In contrast, reinforcer devaluation by removing food restriction substantially decreased both panel pressing and pellet intake. In free-feeding choice tests, mice strongly preferred milkshake vs. pellets. Haloperidol did not affect food intake or preference.
Conclusion
Haloperidol reduced the tendency to work for food, but this reduction was not due to decreases in primary food motivation or preference. Mouse touchscreen procedures demonstrate effects of haloperidol that are similar but not identical to those shown in rats. These rodent studies may be relevant for understanding motivational dysfunctions in humans.