When do astrocytes contribute to the control of brain blood flow?

In order that the brain can function normally, it is essential that blood flow within the brain is well matched to neuronal metabolic demand. When neurons are active they send a message to the local vasculature to increase blood flow (a phenomenon called neurovascular coupling) and so increase the supply of nutrients: glucose and oxygen. This increase in blood flow and blood volume is the basis of non-invasive functional imaging signals such as BOLD fMRI. Understanding how different cells are involved in neurovascular coupling is important not only for understanding what functional imaging signals can tell us about the brain but also for helping us to understand what goes wrong in diseases where neurovascular coupling is altered. We will investigate which cells are involved in controlling brain blood flow under various conditions (e.g. in response to increased neuronal activity, in response to a physiological stimulus). Of particular interest are astrocytes, a supporting cell within the brain. Although astrocytes have been shown to modify the diameter of cerebral arterioles, their role in the regulation of brain blood flow in response to neuronal activity remains controversial.