Total RNA was extracted from bilateral nucleus accumbens and caudate putamen with RNeasy Qiagen mini kit according to the lipid tissue protocol of the manufacturer (Qiagen, Courtaboeuf, France). Messenger (polyA+) RNAs were purified from 500 ng of total RNA using oligo(dT). Libraries were prepared using the strand specific RNA-Seq library preparation TruSeq Stranded mRNA kit (Illumina).