Adolescent nicotine exposure affects later-life nicotine reward and withdrawal in mice

Commencement of smoking at an early age increases the number of cigarettes smoked per day and decreases the likelihood of successful cessation later in life. To date, little is known about the effects that adolescent nicotine exposure has on aspects of nicotine dependence in adulthood. In this study, we examined the effects of adolescent nicotine exposure on nicotine reward and withdrawal in adulthood. Adolescent mice [postnatal day (PND) 28-34] were exposed to nicotine short-term (0.5 mg/kg, subcutaneous (s.c.) twice a day for one day) or repeatedly (0.1 and 0.5 mg/kg, s.c. twice daily for seven days). In adulthood (PND 70) these mice were implanted with osmotic nicotine minipumps for 14 days and 24 h later spontaneous nicotine withdrawal affective (anxiety-like behavior and hyperalgesia) and physical (somatic signs) signs were assessed. Short-term pre-exposure to nicotine during adolescence did not produce alterations in affective or physical nicotine withdrawal signs in adulthood. However, repeated nicotine exposure during adolescence partially reduced nicotine withdrawal signs in adulthood but increases nicotine reward in the conditioned place preference (CPP) test. Interestingly, adult mice exposed to chronic nicotine (0.5 mg/kg,s.c. twice daily for seven days) did not affect nicotine withdrawal signs and reward later in adulthood. This mouse study highlights nicotine exposure during the unique period of adolescence as an important factor for nicotine dependence later in life.