Heatmap of expression of <i>OPRM1</i> splice variant mRNAs among four inbred mouse strains.

The heatmap was generated by clustering Z-scores calculated from the values (Log2 (E−ΔC(t)) of individual variants across different strains/regions using R statistical language (2.15.0) (www.r-project.org), and plotting based upon individual strains within each brain region with enhanced heatmap function heatmap.2 from gplots package. Pfc: prefrontal cortex; Str: striatum; Tha: thalamus; Hyp: hypothalamus; Hip: hippocampus; PAG: periaqueductal gray; BS: brainstem; Cb: cerebellum; Spc: spinal cord; WB: whole brain. 129∶129P3/J; B6: C56BL/6J; SJL: SJL/J; SWR: SWR/J. Expression level was indicated by Z-score.