Treatment day 1: timecourse of effect of acute nicotine (0.5 mg/kg, i.p.) or saline administration on locomotor activity in wild-type (a, c, e, n=15) and α4−/− mice (b, d, f, n=18) over 30 min, as measured by distance traveled (a, b), move time (c, d) and number of moves initiated (e, f). All data are expressed as mean (±SEM). *p<0.05 nicotine-treated compared with saline-treated mice of same genotype, ^p<0.05 α4 −/− mice compared with wildtype within the nicotine-treated group (post-hoc Tukey's tests following two-way repeated measures ANOVA).