Persistent and delayed behavioral changes after nicotine treatment in adolescent rats

Despite the increasing use of tobacco by adolescents, few animal studies ha ve addressed the neurobehavioral consequences of nicotine exposure during t his period. We administered nicotine to adolescent rats via continuous infu sion on postnatal days (PN) 30 through 47.5, using a dosage regimen that ma intains plasma levels similar to those found in smokers or in users of the transdermal nicotine patch. Behavior in a novel open field and learning a p assive avoidance task were assessed during nicotine treatment and for 2 wee ks post-treatment. On PN44, during nicotine exposure, female rats showed de creased grooming, an effect not seen in males; this effect is opposite to t he effects of nicotine in adult rats. Two weeks after cessation of nicotine administration, females showed deficits in locomotor activity and rearing, whereas males again were unaffected; the behavioral deficits appeared at t he same age at which gender-selective brain cell damage emerges. In contras t, nicotine exposure enhanced passive avoidance, with the effect intensifyi ng and persisting throughout the post-treatment period. These results reinf orce the concept that developmental vulnerability to nicotine extends into adolescence, with patterns of drug effects different from those in earlier or later periods. The correlation of neurochemical with behavioral effects strengthens the connection between adolescent nicotine exposure and persist ent functional changes that may influence drug habituation, learning and me mory. (C) 2000 Elsevier Science B.V. All rights reserved.