PT  - JOURNAL ARTICLE
AU  - James E McCutcheon
AU  - Mitchell F Roitman
TI  - Mode of sucrose delivery alters reward-related phasic dopamine signals in nucleus accumbens
AID  - 10.1101/132126
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 132126
4099  - http://biorxiv.org/content/early/2017/04/28/132126.short
4100  - http://biorxiv.org/content/early/2017/04/28/132126.full
AB  - Nucleus accumbens (NAc) dopamine correlates with rewards and reward-predictive cues. However, the mode of reward delivery may have important implications for how reward itself, as well as associated stimuli and behaviours, are encoded by dopamine. We compared two modes of delivery: sucrose pellets, which require goal-directed action for their collection, and intraoral infusions, which require no action. To assess the role of Pavlovian cues in evoking phasic dopamine, rats were trained to associate distinct cues with subsequent delivery of either a sucrose pellet or an intraoral infusion of sucrose solution directly into the mouth. Fast-scan cyclic voltammetry was used to measure phasic dopamine in NAc while rats experienced both cued and uncued rewards within a single session. Behavioural discrimination between pellet-paired and infusion-paired cues was observed with rats making more anticipatory receptacle port entries during pellet-predictive cues than infusion-predictive cues. Both pellet-predictive and infusion-predictive cues evoked dopamine release, however, concordant with the behavioural difference, greater dopamine was evoked by pellet cues than infusion cues. In addition, in cued trials, delivery of pellets increased dopamine above baseline whereas delivery of infusions did not. In uncued trials, both pellets and infusions evoked dopamine release. Responses were generally similar across NAc subregions with core and shell dopamine release appearing qualitatively similar, although dopamine events were broader in shell than in core. Thus, phasic dopamine responses to intraoral infusions and infusion-predictive cues demonstrate a potential role for dopamine in encoding both reward prediction and reward evaluation.