Astrocytes are a key conduit for upstream signaling of vasodilation during cerebral cortical neuronal activation in vivo

摘要

Another unique characteristic of the cerebral circulation relates to the architecture of the arteriolar system. For example, in the cerebral cortex, parenchymal arterioles arise from surface (pial) arterioles, with the two segments linked by penetrating arterioles. Pial arterioles, therefore, represent important upstream vascular segments. However, it is unclear how vaso-dilating signals, originating in cortical neurons, reach the pial arterioles; that is, the pial arterioles overlie a thick layer of astrocytic processes termed the glia limitans. This essentially isolates pial arterioles, anatomically, from the neurons below. Since pial arterioles are known to dilate in association with a variety of neuronal activation models (17) and in light of the seemingly modest or nonexistent influence from shear-related factors (2), this would seem to leave intercellular conduction as a primary mechanism supporting upstream dilation, with vascular cells and astrocytes as the potential signaling conduits.