Vasodynamics of pial and penetrating arterioles in relation to arteriolo-arteriolar anastomosis after focal stroke

Abstract

Changes in blood perfusion in highly interconnected pial arterioles provide important insights about the vascular response to ischemia within brain. The functional role of arteriolo-arteriolar anastomosis (AAA) in regulating blood perfusion through penetrating arterioles is yet to be discovered. We apply a label-free optical microangiography (OMAG) technique to evaluate the changes in vessel lumen diameter and red blood cell velocity among a large number of pial and penetrating arterioles within AAA abundant region overlaying the penumbra in the parietal cortex after a middle cerebral artery occlusion (MCAO). In comparison with two-photon microscopy, the OMAG technique makes it possible to image a large number of vessels in a short period of time without administering exogenous contrast agents during a time-constrained MCAO experiment. We compare vasodynamics in penetrating arterioles at various locations. The results show that the MCA connected penetrating arterioles close to a strong AAA dilate, while those belonging to a region away from AAAs constrict in various degrees. These results suggest AAAs play a major role in supporting the active dilation of the penetrating arterioles, thus compensating a significant amount of blood to the ischemic region, whereas the poor blood perfusion occurs at the regions away from AAA connections, leading to ischemia.