Figure 1.

Acquisition of intravenous cocaine self-administration in adult mice exposed to nicotine (n = 7) or vehicle (n = 8) during adolescence. Both nicotine- and vehicle-exposed mice learned to discriminate between the active and inactive lever by the third day of the acquisition stage. This is indicated by a significantly greater number of active relative to inactive lever presses on days 3 through 5 compared to day 1 (*P < 0.05). Inactive lever presses did not differ significantly across days. Performance of nicotine- and vehicle-exposed mice did not differ significantly during the acquisition stage