Figure 2.

Influence of age of first exposure, strain and sex on nicotine preference two months following initial free choice intake of nicotine. Two months following initial nicotine exposure during early adolescence (a), middle adolescence (b), late adolescence (c), or adulthood (d) mice were retested for nicotine preference. A repeated measures ANOVA demonstrated that age of first nicotine exposure (p = 0.001), strain (p = 1.3 × 10⁻⁵), and sex (p = 0.030) each had a significant effect on nicotine preference in the retested animals. A post hoc analysis further indicated that nicotine preference in re-tested animals first exposed to nicotine during early and middle adolescence was significantly reduced compared to re-tested animals initially exposed to nicotine as adults. Within strain analyses indicated a significant effect of age initially exposed to nicotine on later nicotine preference for C3H/Ibg animals (p = 0.001) (e). A posthoc analysis showed that nicotine preference in re-tested C3H/Ibg mice first exposed to nicotine during late adolescence was significantly more than nicotine preference in animals initially exposed to nicotine during early (p = 0.025) and middle (p = 0.008) adolescence. There was no effect of age initially exposed to nicotine in retested C57BL/6J animals (f). Data represent mean ± SEM.