Age- and ovarian hormone-dependent regulation of genes encoding microglial receptors and their inhibitory neuronal ligands in the rat frontal cortex. TaqMan-based quantitative real-time PCR revealed no change in Sirpa (A), increase in the expression Cd47 (B), decrease in mRNA expression of Cd200r (C), Cd200 (D) and Cx3cl1 (F). Cx3cr1 (E) increased during aging. Error bars show SD of six independent measurements. Statistical significance of the alterations in different groups compared to middle-aged female rats (M) was determined by analysis of variance (ANOVA) with Newman-Keuls post hoc test, and considered 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 OVX rat; M/OVX+E2, middle-aged ovariectomized (OVX) rat treated with 17β-estradiol (E2).