Nicotine exposure during adolescence enhances behavioral sensitivity to nicotine during adulthood in Wistar rats

Abstract

RationaleDrug use during adolescence is associated with an increased propensity for drug dependency during adulthood. Therefore, the effects of adolescent exposure to nicotine on adult behavioral responsiveness to nicotine are of particular importance. ObjectivesThe objective of the current study was to determine if adolescent nicotine exposure would enhance behavioral sensitivity and development of sensitization to nicotine during adulthood. Materials and methodsMale Wistar rats were assigned to one of three groups that received subcutaneous (s.c.) injections of nicotine (0, 0.25, or 0.5mg/kg) in the home cage for 12 consecutive days during adolescence, PD 31–42. Starting on PD 80, distance traveled, rearing, and stereotypy were recorded in locomotor activity chambers each day for 10days, following s.c. injections of 0, 0.25, or 0.5mg/kg nicotine. One week later, a final challenge session took place during which rats were injected with 0.5mg/kg nicotine. ResultsRats exposed to nicotine during adolescence displayed a greater locomotor response to a novel environment than saline-treated rats. Adolescent nicotine treatment also resulted in context-independent sensitization to the acute locomotor activating properties of nicotine, including distance traveled and stereotypy, as measured on the first day of adulthood nicotine exposure. Adolescent nicotine-treated rats displayed increased sensitivity to repeated nicotine exposures during adulthood, compared to adolescent saline-treated rats, as measured by distance traveled, rearing, and stereotypic behaviors. Finally, rats treated with nicotine only during adolescence were more sensitive to a final nicotine challenge during adulthood than rats treated with nicotine only previously during adulthood. ConclusionsOverall, the results suggest that adolescent nicotine treatment predisposes adult rats to develop increased behavioral sensitivity to chronic nicotine treatment and to be more sensitive to the initial effects of nicotine.