Determination of transcript levels (Cq) of the candidate reference genes in the dorsal horn of the spinal cord (A, B) and RVM (C, D). Levels were assessed four days (A, C) or two weeks (B, D) after intraplantar injection of CFA or saline. Values are the mean ± SEM of determinations made in 6–7 rats. In the dorsal horn, no differences were observed in the transcripts levels between saline- and CFA-treated rats, or between four days and two weeks, for any reference gene. In the RVM, transcript levels for each reference gene did not differ between saline- and CFA-treated rats. Although the Cq values at two weeks were statistically different from values at four days, the magnitude of the difference was about 0.2 Cq and unlikely to be biologically significant.