Here, we determined the dynamics of rapid (subsecond) dopamine signaling during cocaine self-administration within the NAc core and shell, and its relationship to NAc cell firing during the same task. In Experiment 1, rapid dopamine signaling was observed within seconds of the reinforced response in both the core and shell, although significant differences were evident in the temporal properties of dopamine release between regions. That is, dopamine responses in the core were closely time-locked to the reinforced response while dopamine events in the shell were of longer duration and less synchronized to the lever-press. In Experiment 2, electrophysiological recordings revealed that a subset of NAc neurons displayed increases and/or decreases in cell firing within seconds of the lever-press for cocaine in both the core and shell, similar to prior reports (Carelli, 2000). However, within both subregions, phasic dopamine release was not uniform but occurred primarily at locations where NAc neurons exhibited patterned activation; additionally, the greater the strength of the neural signal the larger the dopamine release event. Furthermore, it was at those locations that electrically-evoked stimulated release was greatest.
