MA plot of the expression levels of G protein-coupled receptors differentially expressed between healthy and early apoptotic cerebellar granule neurons. Mouse cerebellar granule neurons grown in vitro for 7 days (DIV 7) were incubated for 4 hours in culture medium containing 25 mM (K25) or 5 mM (K5) KCl without serum. GPCR expression levels were determined using real-time PCR, and differentially expressed GPCRs were identified using the Wilcoxon signed-rank test with Benjamini-Hochberg correction. M is the log2-transformed ratio of the normalized expression levels of each GPCR in K5 and K25. A is the log2-transformed maximum of the normalized expression levels of each GPCR in K5 and K25. Red dots indicate those GPCRs that were also identified as differentially expressed in our previous microarray study  using the very same RNA samples. The real-time PCR approach identified more DE GPCRs than microarrays, especially among GPCRs expressed at low to medium levels.