Introduction: Periadolescent nicotine exposure is associated with increased consumption and rewarding properties of abused drugs. In the case of peri- but not post-adolescent animals, these effects are persistent and last to adulthood, suggesting that early nicotine treatment may alter postnatal CNS development in ways that contribute to long-term problems with drug abuse.
Materials and methods: To begin to identify brain regions that may be altered by developmental nicotine exposure, we have measured expression of a transcription factor, FosB, within a series of reward- and memory-related brain regions of Sprague-Dawley rats.
Results: FosB expression is known to acutely and cumulatively increase within a subset of brain regions, particularly nucleus accumbens, after exposure to many classes of abused drugs. Our results demonstrate that FosB is increased within nucleus accumbens and also the granule cell layer of hippocampal dentate gyrus after both peri- and post-adolescent nicotine exposure (0.4 mg kg(-1) day(-1) from days 34 to 43 and 60 to 69, respectively). In periadolescents, expression increases were detected 2 days after nicotine exposure, and persisted for weeks, through at least early adulthood at 80 days of age. In post-adolescents, expression increases persisted for at least 11 days to postnatal day 80.
Discussion: These findings demonstrate that nicotine treatment during both peri- and post-adolescence persistently alters activity of brain regions involved in reward and memory.
Conclusion: Because this altered gene expression occurs after both peri- and post-adolescent treatment, it cannot be directly responsible for increased consumption and rewarding properties of abused drugs previously established to be distinctly associated with periadolescent nicotine exposure.