Abstract:
Tobacco use is one of the leading health concerns in the world. Of particular concern is the unique vulnerability that adolescents exhibit for nicotine use and addiction which has been examined via animal models. This project examines the effects that a single injection of nicotine has on early adolescent, late adolescent, and adult Long-Evans male rats. Rats were initially tested in the elevated plus maze at P28, P45, and P80 as a screen for anxious behavior. The next day, all animals received a saline injection and were placed in the open field to determine baseline locomotor behaviors. On Day 3, all animals received a single injection of nicotine (0.4 mg/kg, s.c., freebase) and locomotor variables were again determined. Twenty-four hours after nicotine injection, rats were sacrificed and tissue targeting the nucleus accumbens was sliced using a cryostat. In situ hybridization was completed to analyze the expression of D2 mRNA in the core and shell of the nucleus accumbens. When all three age groups were compared to each other, adults in the elevated plus maze spent more time in the center than either early or late
adolescents. In the open field, early adolescents traveled more total distance than either late adolescents or adults and traveled more distance in the center than adults. Using the data from these two behavioral tests, simple regression equations could be calculated that were predictive of D2 mRNA expression in the core and shell among early adolescents and adults. Interestingly, elevated plus maze variables were more predictive of D2 expression in early adolescents and open field variables were more predictive of D2 expression in adults. This suggests that a rat’s expression of D2 mRNA in the NAc core and shell may be related to differential behavioral variables at different age points.
