The publicly available microarray experiment dataset GSE7762 was designed to determine the impact of genetic background on the transcriptional effects of morphine in mouse striatum (19). It used different morphine treatments, including a single morphine injection of 20 mg/kg, repeated (3 times daily for 5 days) morphine injections of 10-40 mg/kg, and saline, in four inbred mouse strains (129P3/J, DBA/2J, C57BL/6J and SWR/J). We used the R package GEOquery (20) to download the normalized GSE7762 microarray data from GEO and analyze the expression of Rgma (the mouse gene homologous to RGMA). One-way ANOVA implemented in MATLAB (Statistics Toolbox Release 2015b, MathWorks, Inc., Natick, Massachusetts, United States) was used to test the effect of morphine on Rgma expression in different mouse strains. Statistical significance was set at P<0.05.
