Age- and ovarian hormone-dependent regulation of genes encoding toll-like receptors and co-receptor Cd14 in the rat frontal cortex. TaqMan-based quantitative real-time PCR revealed changes in mRNA expression of Tlr4 (B) and Tlr9 (C). Tlr2 (A) and Cd14 (D) did not alter. Error bars show SD of six independent measurements. Statistical significance of the alterations in different groups compared to middle-aged female rats (M) was calculated using analysis of variance (ANOVA) with Newman-Keuls post hoc test, and considered significant at P < 0.05. Asterisks indicate changes with statistical significance: * corresponds to 0.01<P < 0.05, ** to 0.001<P < 0.01 and *** to P < 0.001. Y, young rat; M/OVX, middle-aged ovariectomized (OVX) rat; M/OVX+E2, middle-aged OVX rat treated with 17β-estradiol (E2).