Novel Optical Imaging Approach to Study Neurovascular Coupling System

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Understanding the relationship between neural activity and Blood-brain barrier (BBB) permeability is important to integrate our knowledge of neurovascular coupling system. Although much effort is focused in understanding the underlying mechanisms that regulate blood flow in response to neural activity5, little is known about how neural activity regulates tissue perfusion. Direct in vivo measurements of Ca2+ dynamics in cerebral blood vessel cells and quantification of BBB permeability have been difficult largely due to technical limitation. Researchers have been using bulky fluorescence-labeled solutes for conventional studies on BBB permeability. However, bulky fluorescence labeling perturbs the structural and functional properties of the biomolecules and suffered from photo bleaching. For these reasons, tiny Raman tagged molecules combined with SRS imaging is ideal for studying BBB permeability in vivo. Here we propose a novel optical imaging approach to determine the relationship between neural activity and BBB permeability in vivo. The main thrust of this proposal is to use a combination of bioorthogonal probed stimulated Raman scattering (SRS), multi-photon fluorescence, and mouse genetics to obtain simultaneous measurements of Ca2+ activity and BBB permeability. Vascular endothelial cells will be labeled with a genetically encoded calcium indicator while bioorthogonal-tagged molecules with specific vibrational modes will be injected into the brain vasculature to measure the BBB permeability, and the relationship between calcium dynamics and permeability of the BBB will be studied. Successful completion of the aims described in this proposal will enable a novel framework for future mechanistic studies of in vivo BBB permeability in animal models for blood vessel development and vasculature diseases.