ABSTRACT
The blood brain barrier (BBB) has been viewed classically as a barrier that separates blood and brain compartments, providing nutrients and other essential molecules to the brain while protecting brain cells from potentially harmful agents in the blood. However, it has become clear that this is an overly simplistic view. We now know that the cerebral microvascular endothelial cells of the BBB provide a highly dynamic interface between blood and brain. Further, BBB endothelial cell function is inextricably linked to the functions of other cells in the neural environment, including at the most basic level, perivascular astrocytes, pericytes, microglia and neurons. With increasing awareness of these important cellular interactions, the term neurovascular unit (NVU) came into use. The majority of brain pathophysiology studies in the past have had either a neurocentric or vasculocentric focus with the disappointing result that very few successful therapies were identifi ed. If we are to better understand how cells of the brain function in health and disease, we must consider the function of each of these cell types in the context of the entire community of cells that comprise the NVU. This chapter will consider different functional aspects of the cells within the NVU and how their interactions subserve various physiological functions of the brain. An area of great importance to the BBB and NVU is that of solute and water movements that occur between blood and brain and among the cells of the NVU in both health and disease. In this regard, the following sections will highlight the mechanisms responsible for moving nutrients, metabolites, xenobiotics, ions and water throughout the NVU and how these support brain function and/or contribute to pathology in disease.
