Closed cranial window applications in the rat: Studies on neurovascular coupling involving pial arterioles and the glia limitans

Abstract

Because of their intimate anatomic relationship with cerebral arterioles and neurons, astrocytes have been postulated to function as signal transducers, transferring information from activated neurons to the cerebral microcirculation. The above is labelled as “neurovascular coupling” and its components (i.e., neuron, astrocyte, and vascular cells) as the “neurovascular unit (NVU).” In the brain, NVUs can take a variety of forms. In the chapter, we highlight a well-represented cortical NVU consisting of pial arterioles, the glia limitans, and cortical neurons. This particular NVU can be readily examined in vivo using a closed cranial window system that permits one to monitor pial arteriolar diameter changes and manipulate astrocytic influences during periods of enhanced synaptic activity. In addition, this model can be used to evaluate mechanisms of upstream arteriolar relaxation. This dilation is necessary during periods of increased metabolic demand, in order to permit more blood to reach dilated downstream vessels, thereby improving nutrient supply to the activated neurons. Without pial arteriole dilation, downstream dilation in the vicinity of active synapses may be ineffective, placing neurons at risk, especially during episodes of intense neuronal activity, such as seizure.