Delayed extinction and stronger reinstatement of cocaine conditioned place preference in adolescent rats, compared to adults.

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Abstract
Adolescence is a transitional period during development that is associated with a greater likelihood of addiction to drugs than any other age. One possibility for this observation is that learned associations between the rewarding experience of drugs and drug-related cues may produce greater motivational salience, and thus are more difficult to extinguish. Using an unbiased place-conditioning paradigm with two doses of cocaine (10 mg/kg or 20 mg/kg), the authors show here that adolescents require 75 +/- 17% more extinction trials than adults to extinguish cocaine place-preferences. Furthermore, once extinguished, adolescents display a greater preference for a previously cocaine-paired environment upon drug-primed reinstatement compared with adults. These results suggest that adolescent vulnerability to addiction involves robust memories for drug-associated cues that are difficult to extinguish. Therefore, drug-addicted adolescents may have a higher risk of relapse than adults, leading to greater prevalence of addiction in this population.