Total RNA containing the small RNA fraction was isolated from 100mg of frozen tissue from the nucleus accumbens (NAc) using the mirVana-PARIS kit (Life Technologies, Carlsbad, CA), following manufacturer's protocols. RNA concentration was measured using the Quant-iT Broad Range RNA Assay kit (Life Technologies), and the RNA Integrity Number (RIN) was measured on the Agilent 2100 Bioanalyzer (Agilent Technologies, Inc., Santa Clara, CA). All subjects were initially included for matching based on age, sex, ethnicity, brain pH, PMI and RIN, and this yielded 18 appropriately matched case-control pairs with RINs ≥6 (N = 36).
