Abstract: Cells of the central nervous system (CNS) are privileged in lying behind the blood–brain barrier (BBB). Unlike blood vessels in other organs, CNS blood vessels are unique in displaying high electrical resistance and low permeability. With this unique structure and function, the BBB prevents potentially harmful blood components such as serum proteins, inflammatory cytokines, and inflammatory leukocytes from entering the hallowed space of the CNS and wreaking havoc. In addition to these “tightness” properties, the BBB has an array of specialized transporters designed to import essential nutrients, such as amino acids and glucose into the CNS. It also has transporters that remove unwanted chemicals or drugs from the CNS called multidrug resistance proteins, such as P-glycoprotein. At the structural level, the BBB consists of a lining of endothelial cells firmly attached to a basement membrane (BM) containing high levels of the extracellular matrix (ECM) proteins collagen IV, laminin, fibronectin, and perlecan. Pericytes and astrocyte foot processes also play an important role in inducing and maintaining BBB properties. At the molecular level, the BBB relies on adhesion molecules (primarily integrins) that bind endothelial cells to the BM as well as adherens and tight junction protein complexes that form between adjacent endothelial cells (Zlokovic, 2008). The importance of the BBB is illustrated by the fact that its disruption is instrumental in the initiation and/or maintenance in almost all neurological diseases, including ischemic stroke, multiple sclerosis, vascular dementia, and Alzheimer’s disease. Aside from deteriorating during disease conditions, accumulating evidence suggests that BBB integrity also declines as a function of age (Senatorov et al., 2019).