Glial Laminar Cortical Architecture Matches Metabolic Demand

Abstract

The link between increased neural activity and cerebral blood flow is well established (Roy and Sherrington, 1890); yet, the mechanism by which blood flow is matched to neuronal activity both spatially and temporally is unclear. Based on their morphology, gray matter (protoplasmic) astrocytes are ideally situated to translate regional synaptic activity to hyperemia (increased flow) as they extend processes that envelop both synapses and vasculature (reviewed in Iadecola and Nedergaard, 2007). Indeed, evidence from in vitro and in vivo two-photon imaging has suggested that stimulus-induced elevations in astrocyte intracellular calcium are positioned to modulate vascular tone (Zonta et al, 2003; Takano et al, 2006; Mulligan and MacVicar, 2004; Winship et al, 2007). These local interactions are purported to occur at the astrocytic endfoot–blood vessel interface (reviewed in Iadecola and Nedergaard, 2007). Regionally, the spatial organization of astrocytes and vasculature should also have implications for matching blood flow to activity. While previous works have examined the interrelationships between astrocytes and microvasculature across cortical lamina, these studies have been conducted using histology and thus may not always faithfully represent the living tissue (White et al, 1981; Tsai et al, 2009). The present work of McCaslin et al (2010) has taken an important step to extend these findings in the live murine brain.