Relative expression of sodium channel isoform mRNA in lamina I/II lumbar spinal cord. qRT-PCR was performed on superficial horizontal dorsal horn slices of Wistar rats using sodium channel isoform-specific primers and normalization to an endogenous control (actin). A) Left, comparisons between sodium channel isoform expression relative to NaV1.7 revealed predominant expression of NaV1.2 and NaV1.3 isoforms in P6 to P9 rats (n = 5). Right, relative expression for the sodium channel isoforms that are robustly expressed within lamina I/II tissue compared to isoform expression within DRG tissue or lamina III to X spinal cord tissue. Note the logarithmic scale used to differentiate between less (negative) or more (positive) isoform expression relative to the tissue under comparison. The error bars represent ranges that are functions of the standard deviations of the ΔΔCT values (see Methods). B) Similar expression profiles for sodium channel isoforms were observed for lamina I/II spinal cord tissue taken from more mature Wistar rats (P25 to P30; n = 5).