Mode of Sucrose Delivery Alters Reward-Related Phasic Dopamine Signals in Nucleus Accumbens

• Published in: ACS chemical neuroscience Vol. 10; no. 4; pp. 1900 - 1907
• Main Authors: McCutcheon, James E, Roitman, Mitchell F
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.04.2019
• Subjects: Animals; Conditioning, Classical - drug effects; Conditioning, Classical - physiology; Cues; Dopamine - metabolism; Male; Motivation - drug effects; Motivation - physiology; Nucleus Accumbens - drug effects; Nucleus Accumbens - metabolism; Random Allocation; Rats; Rats, Sprague-Dawley; Reward; Sucrose - administration & dosage; voltammetry; Rat; pellet; intraoral; sugar
• ISSN: 1948-7193; 1948-7193
• DOI: 10.1021/acschemneuro.8b00262

In studies of appetitive Pavlovian conditioning, rewards are often delivered to subjects in a manner that confounds several processes. For example, delivery of a sugar pellet to a rodent requires movement to collect the pellet and is associated with sensory stimuli such as the sight and sound of the pellet arrival. Thus, any neurochemical events occurring in proximity to the reward may be related to multiple coincident phenomena. We used fast-scan cyclic voltammetry in rats to compare nucleus accumbens dopamine responses to two different modes of delivery: sucrose pellets, which require goal-directed action for their collection and are associated with sensory stimuli, and intraoral infusions of sucrose, which are passively received and not associated with external stimuli. We found that when rewards were unpredicted, both pellets and infusions evoked similar dopamine release. However, when rewards were predicted by distinct cues, greater dopamine release was evoked by pellet cues than infusion cues. Thus, dopamine responses to pellets, infusions as well as predictive cues suggest a nuanced role for dopamine in both reward seeking and reward evaluation.