Accumbal Dopamine Release Tracks the Expectation of Dopamine Neuron-Mediated Reinforcement

Abstract

Dopamine (DA) transmission in the nucleus accumbens (NAc) facilitates cue-reward associations and appetitive action. Reward-related accumbal DA release dynamics are traditionally ascribed to ventral tegmental area (VTA) DA neurons. Activation of VTA to NAc DA signaling is thought to reinforce action and transfer reward-related information to predictive cues, allowing cues to guide behavior and elicit dopaminergic activity. Here, we use optogenetics to control DA neuron activity and voltammetry to simultaneously record accumbal DA release in order to quantify how reinforcer-evoked dopaminergic activity shapes conditioned mesolimbic DA transmission. We find that cues predicting access to DA neuron self-stimulation elicit conditioned responding and NAc DA release. However, cue-evoked DA release does not reflect the cost or magnitude of DA neuron activation. Accordingly, conditioned accumbal DA release selectively tracks the expected availability of DA-neuron-mediated reinforcement. This work provides insight into how mesolimbic DA transmission drives and encodes appetitive action. To understand how mesolimbic dopamine signaling drives and encodes reward learning and seeking, Covey and Cheer recorded nucleus accumbens dopamine release while mice performed optogenetic self-stimulation of dopamine neurons. Cues that motivated self-stimulation elicited dopamine release, which reflected the availability, but not the expected cost or magnitude, of dopamine neuron activation. Copyright 2019 The Author(s)