KOR or Dynorphin KO mice show increased vascular formation in brain and intersomitic vessels. (A) Representative results of WT, PDYN KO, and KOR KO mouse embryo at E10.5. Whole-mount CD31 (red) staining. Left, WT mice. Pn, perineural vascular plexus; Isv, intersomitic vessels. Middle, PDYN KO mice. Right, KOR KO mice. Scale bars, 2 mm. (B) High-magnification views of CD31-stained Pn region. Scale bars, 200 μm. (C) Greater magnification views corresponding to boxed regions in panel B. Scale bars, 40 μm. (D) Quantitative evaluation of CD31⁺ area in Pn. CD31 staining of WT mice was set as 1.0. (n = 3, **P < .01 vs WT). (E) Flow cytometry. X-axis: VE-cadherin; y-axis: CD31. Percentages of CD31⁺/VE-cadherin+/CD45⁻ ECs in the embryo are indicated. (F) Quantitative evaluation of CD31⁺/VE−cadherin⁺/CD45⁻ ECs in the embryo. (n = 3, *P < .05 vs WT). (G) Quantitative RT-PCR showing mRNA expression in purified CD31⁺/VE-cadherin⁺/CD45⁻ ECs in the embryo. WT mRNA expression was set as 1.0. (n = 3, **P < .01 vs WT). (H) High-magnification views of CD31-stained Isv region in E10.5 embryo. Ectopic invasion of Isv into somite was observed in both KO mice. Scale bars, 100 μm. (I) Quantitative RT-PCR showing mRNA expression in purified CD31⁺/VE⁻cadherin⁺/CD45⁻ ECs in the embryo. WT mRNA expression was set as 1.0. (n = 3, **P < .01 vs WT).