Figure 2.

Real-time dopamine transmission patterns during early acquisition of a cue-cocaine association. A and C) Mean change in [DA] is represented as change in color during the 90 s sampling window (x-axis) for each conditioning trial (y-axis). The i.v. cocaine infusion (3 s) is represented by the dark grey box and the predictive cue (20 s) is represented by the light grey box. B and D) Quantification of [DA] within the NAc core and shell during cue-cocaine association. Trial numbers are indicated on the figure and dopamine concentrations were binned in 2.5 s intervals. A) Within the NAc core (n = 5), cue-evoked dopamine release is increased across conditioning trials. Cocaine-evoked increases in [DA] were present early in the conditioning session but inconsistent thereafter. B) Within the NAc core (blue; n = 5), [DA] was not altered during the first conditioning block (trials 1 to 10) by either cue presentation or cocaine infusions. However, during the second (trials 11 to 20) and third conditioning blocks (trial 21 to 30), [DA] was significantly increased during cue presentation with dark blue bars indicating a significant increase over the the pre-cue/infusion baseline (i.e. the first four bins) (p < 0.05). C) Within the NAc shell (n = 5), [DA] is lowest during cue presentation and the cue-evoked attenuation in [DA] was present from the onset of the conditioning session. Cocaine robustly increased [DA] at later time points consistent with its known pharmacokinetics. Cocaine-evoked dopamine release continued following multiple drug infusions and [DA] levels were highest toward the end of the session. D) Within the NAc shell (light orange; n = 5), [DA] was significantly decreased (indicated by white bars) during cue presentation during all conditioning blocks. In the final conditioning block (trials 21 to 30) [DA] was significantly increased (dark orange) over the pre-cue/infusion baseline (p < 0.05) (beginning 20 s after drug infusion). B and D) error bars equal standard error from the mean.