Fig. 3.
a, b Representative LSCI-derived image sequences of speckle contrast showing flow on the cortical surface before and after dMCAo. Images showing flow changes over 270 min (4.5 h) post are illustrated for aged (a) and young adult rats (b). Immediately after dMCAo, robust anastomotic connections between distal segments of the ACA and MCA become visible in both groups (see yellow arrowheads showing absent or low flow in distal ACA-MCA anastomoses before stroke (left-most panel) and enhanced flow after dMCAo in next panel). Pial collaterals were more robust and persistent in young adult rats (n = 11) relative to aged rats (n = 11). Note the consistent increase in speckle contrast during the imaging period in the aged rats (a), which reflects decreasing flow over time, and relatively few visible pial vessels. Contrasting this decreased flow in aged rats, speckle contrast remains relatively stable during imaging after stroke in young adult rats (b). Speckle contrast (k) and relatively blood flow (1/k2) for aged and young adult rats are shown in (c) and (d), respectively. Two-way ANOVA on k and 1/k2 identified significant main effects of age and time × age interactions (all P < .0001), and post hoc comparisons identified significantly group differences at all time-points 60 min or more after ischemic onset in both measures. * P < .05, ***P < .001, **** P < .0001