We previously reported similar coincident changes in rapid dopamine release and phasic NAc cell firing during ICSS that were reversed via iontophoretic application of a dopamine D1 receptor antagonist (Cheer et al., 2007). Although iontophoretic drug application was not attempted here due to cocaine-induced stereotypy, significant linear regressions were obtained between the strength of the neural code for phasically active cells and dopamine release events. These findings support the view that rapid dopamine signaling may indeed be modulating the activity of NAc neurons during behavior. Interestingly, ongoing studies in our laboratory indicate similar relationships between rapid dopamine release and NAc cell firing during food-reinforced behaviors. Thus, our findings reveal that the NAc (both the core and shell) is a functionally heterogeneous structure and that rapid dopamine release is anatomically situated, and released at unique periods, to play a critical role in the activation of NAc neurons that encode reward-directed behaviors.
