Enhanced nicotine-seeking behavior following pre-exposure to repeated cocaine is accompanied by changes in BDNF in the nucleus accumbens of rats

► Evaluation of locomotor activity, nicotine self-administration and gene expression. ► Molecular assays to evaluate gene expression in the nucleus accumbens. ► Cocaine caused locomotor sensitization and cross-sensitization with nicotine. ► Repeated cocaine injections increased the break point and total nicotine intake. ► Cocaine and nicotine interaction increased BDNF gene expression in the accumbens.