Nicotine-induced conditioned place preference in adolescent and adult rats

About 1 million American adolescents start smoking every year. Adolescents may be unusually sensitive to certain consequences of nicotine, demonstrating, for instance, significantly higher rates of dependence than adults at the same level of nicotine use. To explore whether adolescents may be more sensitive to rewarding properties of nicotine than adults, the present study used an animal model to assess the rewarding effects of a low nicotine dose (0.6 mg/kg) in a conditioned place preference (CPP) paradigm. Locomotor activity during conditioning and testing was also evaluated. Nicotine was observed to induce place preference conditioning in adolescent Sprague-Dawley rats, whereas the training dose of 0.6 mg/kg failed to produce convincing place preference in their adult counterparts. Age differences were also apparent in terms of nicotine influences on motor activity, with adults being more sensitive to nicotine-suppressant effects and only adolescents showing an emergence of nicotine-stimulatory effects upon repeated exposures. An increased predisposition to stimulatory nicotine effects during adolescence may contribute to age-specific rewarding properties of the drug as revealed using the CPP paradigm in this experiment. Increased sensitivity to stimulatory and rewarding effects during adolescence could potentially contribute to the high rate of nicotine use and dependence among human adolescents. (C) 2002 Elsevier Science Inc. All rights reserved.