P2X7 (A) and P2Y6 (B) mRNA expression in microglia is lower at 3 days than at the other ages. P2R mRNA levels in freshly-isolated microglia from male and female mice of different ages and mixed-sex primary neonatal microglial cultures were determined using qRT-PCR. Expression was normalized to β-actin and average folds (+/- SEM) are graphed relative to the 3d time point of each sex. n = 4–6; for primary cells n = 5 separate culture preparations. #0.05 < p ≤ 0.10; * p ≤ 0.05; ** p ≤ 0.01; *** p ≤ 0.005. Primary cultures: a - 0.05 < p ≤ 0.1 vs. freshly-isolated microglia.