Age differences in conditioned place preferences and taste aversions to nicotine

Adolescence is a critical time in development during which the brain undergoes rapid development. There are marked developmental differences in behavior and neuronal activity that suggest that adolescents are more likely than adults to begin and sustain using drugs of abuse such as nicotine. The current experiments were designed to assess age differences in (1) the rewarding and aversive properties of nicotine via a combined conditioned taste aversion (CTA)/conditioned place preference (CPP) paradigm, (2) aversive properties alone via a CTA paradigm, and (3) immediate early gene expression in the hippocampus (HPC), nucleus accumbens (NAc), and ventral tegmental area (VTA) via real-time RT-PCR following exposure to a nicotine drug challenge. Adolescents displayed a greater preference for a nicotine-paired environment compared to adults, and a weaker taste aversion to lower doses of nicotine. Although RT-PCR analysis in the NAc revealed no age or dose effects, analysis of HPC and VTA revealed a nicotine-induced increase in c-fos and NGFI-B expression in VTA, with adolescents expressing higher levels of c-fos message in HPC but lower levels of NGFI-B in both HPC and VTA than adults. These studies demonstrate age related sensitivities to opposing effects of nicotine that likely reflect alterations in gene expression within the rat brain.