Figure 6. Hippocampal microarray analyses and comparisons to prior aging studies.

P-value histogram derived from the results of the two-way ANOVA (age and drug) reveals robust aging, but not drug or interaction effects. Changes in hippocampal microarray gene signatures were separated according to main effects of age, drug, or interaction (age×drug). While more genes than expected by chance (dashed horizontal line) were shown to be age-sensitive (819, bold line), fewer than expected by chance were found to be PIO-sensitive (189, dotted line), or associated with the interaction (125, gray line) (median FDRs for age = 0.21; for drug = 2.3; for interaction = 3.8). Dataset was derived from hippocampal tissue isolated from 6–8 animals per group. Inset: Agreement of age-related hippocampal gene expression across this and prior studies. Genes found to be present and annotated across four studies (3906) were subjected to overlap analysis for common age-related transcriptional profiles. Unified aging list includes genes found to change three studies [47], [48], [50]. Here, the number of genes expected to overlap by chance (94 up, 36 down) was significantly greater (151 up and 61 down; p<0.01). * indicates p<1.7E-8 for up and p<2.7E-4 for downregulated genes.