The day after steady nicotine self-administration (FR1) had been achieved, animals received (±)TCP (3 mg/kg, i.p.; black bars) or (+)TCP (1.5 mg/kg, i.p.; white bars) pretreatment and 45 min later either a saline (0.5 ml/kg, s.c.) or mecamylamine injection (1, 3 or 5 mg/kg, s.c.). Fifteen minutes later animals were allowed to self-administer nicotine (7.5 μg/kg/inj.). Mecamylamine had no affect in the (±)TCP-trained group (n=6/group), but caused a significant drop in responding in the (+)TCP-group (*p<0.05; **p<0.005 vs. baseline, n=6–7/group). Mean reinforced responses (+SEM) were plotted for each treatment group.