Comparison of mRNA levels of IR signaling proteins in rod- and cone-dominant retina. Equal amounts of retinal mRNA from three independent Nrl−/− and C57BL/6 mice were used for real-time RT-PCR and normalized by 18 S rRNA levels. mRNA levels were averaged for 4E-BP1, Grb14, IGF1-R, IR, mTOR, p110α, p85α, PTP1B, P70S6K, Src, cone-Tα, middle wavelength (MWL) cone opsin, rhodopsin, rod Tα, and short wavelength (SWL) cone opsin. Each mRNA level in Nrl−/− and C57BL/6 mice was expressed as normalized -fold expression (normalized by 18 S rRNA). The data are the mean ± S.D. n = 3. **, p < 0.05; *, p < 0.001.