Effects Of Age And Nicotine Pretreatment On Spatial Discrimination In Male Rats

Adolescence is the developmental period between childhood and adulthood, in which the brain undergoes critical maturation and remodeling. It is also a time of increased vulnerability for the initiation of tobacco use, thus making the developing neural circuits vulnerable to the effects of drugs. Previous work from our lab suggests that the dentate gyrus (DG), which mediates spatial learning, may be affected by nicotine exposure during adolescence. Adolescent rats treated with nicotine had altered brain maps of coordinated gene expression (CGE) for cfos mRNA between the DG and motor output/planning regions. The purpose of the present study was to determine if maps of CGE could predict alterations in function of the DG. Nicotine (0.06mg/kg/day) or saline was intravenously infused into adolescent (postnatal day (P) 28-31) and adult (P86-P89) male Sprague-Dawley rats for four consecutive days. On P32 for adolescents and P90 for adults, animals were placed in novel open field activity chambers, where they would perform a metric change in object location task. They were allowed to habituate to the experimental room for 15 minutes. Locomotor and behavior activity were then recorded for 30 minutes. Adolescent nicotine-pretreated rats spent significantly more time with the objects in trial 4 than those pretreated with saline. There was also a significant increase in horizontal counts in the object-containing quadrants (Q3 & Q4). This effect was unique to adolescents. Nicotine pretreatment had no effect on adults. Our results suggest maps of CGE correctly predicted that adolescents’ spatial learning is uniquely affected by nicotine pretreatment.