Figure 2: PO₂ distribution measured inside the penetrating arterioles during normocapnia.

(a) Maximum intensity projection of the microvascular structure obtained by TPM showing diving arteriole at the centre (red arrow). Scale bar, 50 μm. (b) PO₂ map inside the penetrating arteriole in a, 100 μm below the cortical surface. Scale bar, 20 μm. Inset in the upper left-hand side of b shows a two-dimensional image from a microvascular stack (a) at the PO₂-imaging depth (100 μm below the cortical surface). (c) Radial intra-arteriolar PO₂ profiles (radial distance calculated from the vessel axis (vessel centre) to the vessel wall) from four penetrating arterioles similar to the example vessel presented in a and b. For each PO₂ profile, a star indicates the smallest radius where the mean PO₂ is significantly lower than the PO₂ at the vessel centre (two-sample t-test; P≤0.034). Data are expressed as mean±s.e.m., calculated as detailed in the methods. Results are presented for n=3 mice.