GPR81 levels during developmental cerebral angiogenesis. (a) GPR81 expression (150 bp) evaluated by reverse-transcriptase-PCR was detected in brain homogenates from WT mice, but it was absent in brain samples from GPR81-null mice; 18S (187 bp) was used as an internal control. Real-time quantitative PCR was used to determined ontogenic expression of GPR81 at different postnatal (P) ages (P5, P7, P9, P11 and P15). Data represent mean ± SD; n = 6 animals per group; *p < 0.05, **p < 0.01 compared to P5, one-way ANOVA followed by the Dunnett’s test for multiple comparison with control. (b) Western blot analysis of GPR81 (39 kDa) expression levels in brain samples from WT mice at different postnatal ages (P5, P7, P9, P11 and P15). Vinculin (110 kDa) was used as internal controls. Data represent mean ± SD; n = 5 animals per group. **p < 0.01 compared to P5; one-way ANOVA followed by the Dunnett’s test for multiple comparison with control.