Mean reinforced responses as a percentage of baseline (+ SEM) were plotted for each treatment group. The day after steady nicotine self-administration (FR1) had been achieved, either the nicotine (7.5 μg/kg/inj, i.v.) solution was replaced with saline (i.v.) (white bars) or the house and cue lights were inactivated (gray bars) during the self-administration sessions. A. (±)TCP-trained animals showed no change in responding after saline was substituted for nicotine (Sal + Cues), but significantly decreased responding after cues were eliminated (Nic + No Cues; *p<0.05 vs. Baseline (Nic + Cues), n=6/group). B. Conversely, (+)TCP-trained animals decreased responding following saline (i.v.) substitution (**p<0.01 vs. Baseline (Nic + Cues), n=7–9/group), but not after cue elimination.