The effects of acute, chronic, and withdrawal from chronic nicotine on fear conditioning in pre-adolescent, adolescent, and adult mice. A: Compared to adults, pre-adolescent mice were more sensitive to the effects of acute nicotine on contextual fear conditioning whereas adolescent mice were less sensitive. B: Pre-adolescent mice exhibited enhanced contextual fear conditioning when treated with 12 mg/kg/d chronic nicotine. C: Compared to adults, pre-adolescent mice were less sensitive to the effects of nicotine withdrawal on contextual fear conditioning whereas adolescent mice were more sensitive. No significant changes in cued fear conditioning were observed. Error bars indicate SEM, (*) indicates p < 0.05.