ABSTRACT Endothelial cells (ECs), astrocytes and pericytes are integral components of the neurovascular unit (NVU) and play critical roles in blood brain barrier (BBB) formation and maintenance. These cells express uptake and efflux membrane transporters that regulate CNS penetration of molecules, therapeutic drugs and toxins. The function of the BBB and transporters is likely disrupted in many neurological disorders. Thus, development of tools to study NVU cells and their properties of BBB selective transport in vivo is a key priority in translational neuroscience research. We have discovered a unique set of small molecules that can be selectively transported into the cytoplasm of either ECs, pericytes or astrocytes with exquisite affinity and specificity. We have evidence that these molecules enter cells through membrane transporters, selectively expressed in each cell type. We hypothesize that these molecules could be adapted as probes for intravital animal and human imaging and also for cell-specific delivery of drugs. In this proposal, we aim to identify the precise mechanisms of probe membrane transport in vivo; establish the feasibility of using these molecules as cell-specific drug carriers or as radiopharmaceuticals for human imaging with positron emission tomography (PET) and finally test their in vivo properties in models of Alzheimer's disease and stroke. This project will improve our understanding of molecular transport mechanisms across the BBB and may transform the ability to selectively image and pharmacologically modulate cells of the NVU in health and disease.