Effects of nicotine on the development of locomotor sensitization to 1 g/kg ethanol. Shown is mean (± SEM) total distance traveled during the first 5 min of each 15-min locomotor activity test session. On day 1 and 2, mice received saline. On day 3 –12 (acquisition period) mice were treated with SAL, E1, N1, N2, E1+N1, or E1+N2 once daily, with locomotor activity assessed every third day. On day 13 (ethanol challenge), all mice were treated with 1 g/kg ethanol alone. Group labels show treatment during acquisition with day 13 treatment in parentheses. N1 and N2 = 1 or 2 mg/kg nicotine tartrate; E1= 1 g/kg ethanol; SAL=saline.