Triplicate Northern slot blots for three genes with altered expression, 2 showing an increase after axotomy (A and B), one a decrease (C). Cyclophilin a gene known not to alter following axotomy shows equal loading of the slot blots and acts as a normalization control (see methods) (D). The histograms indicate the Northern slot blot data expressed as percentage of naïve expression levels or above the graphs as fold change. Below the blots is the gene expression fold change calculated from the triplicate microarray data. ** P < 0.01, * P < 0.05 (two-tailed unpaired t-test). E. Correlation between 19 separate mRNA fold-differences calculated by triplicate slot blot and those calculated from the triplicate arrays. Linear regression line of best fit is also plotted, scale does not represent values between -1 and 1 as fold change values within this range do not exist due to the method of calculation (see methods).