RNA was extracted from whole brain of three naïve male rats per strains using the the miRNeasy Mini and RNeasy MinElute Cleanup Kits (Qiagen, Valencia, CA, USA). Sequencing libraries were constructed using the Illumina TruSeq RNA Sample Preparation kit from 1 ug RNA according to manufacturer's instructions. Library quality was assessed using the Agilent Bioanalyzer 2100 (Agilent Technologies, Santa Clara, CA, USA). Samples were sequenced (2x100 paired-end reads) on the Illumina HiSeq2000. Samples were multiplexed over 3 lanes of the flowcell (2 lanes with 3 samples each and 1 lane with all 6 samples).