Figure 2.

A spectrum of cortical infarct volumes induced by targeted photothrombotic occlusion of single penetrating arterioles. (a) Schematics depicting the placement of the green laser focus for occlusions of cortical penetrating arterioles (on-target; right) or control irradiations (off-target; left). (b) In vivo two-photon images of the pial surface before and after targeted irradiation. Non-flowing vascular segments are colored in yellow. Only the pre-occlusion image is shown for the off-target irradiation because no loss of pial vessel flow was observed. (c) NeuN immunohistology to quantify the volume of tissue infarct resulting from single penetrating arteriole occlusions or off-target irradiations. The white matter of the external capsule is labeled, wm, to show the base of the cortex. (d to f) Scatter plot of infarct diameter, depth and volume versus the pre-occlusion RBC volume flux of individual penetrating arterioles. Infarct diameter and volume, but not depth, were significantly correlated with flux (n = 18). Off-target irradiations generated infarcts volumes over an order of magnitude smaller than penetrating arteriole occlusions (p < 0.001, Mann-Whitney test). Since no penetrating vessel was occluded with off-target irradiation, there is no associated flux to report. The crossbars show mean ± SEM for all data points in each irradiation group. Regression analyses of penetrating arteriole occlusion data were performed on log10-transformed values. (g) Schematic showing relative infarct size between off-target irradiations and on-target occlusions, based on average values from panels (d) to (f).