Testing of the VTA - EC Ca2+ – BBB Hypothesis - Abstract In complex natural environments, optimal behavior requires a precise understanding of body state. However, information transmission between body and brain is limited by the blood-brain barrier (BBB). Chiefly comprised of tightly coupled Endothelial Cells (ECs), this barrier is canonically considered a static blockade to most molecules during health. Preliminary Data from our lab shows that, in contrast to this canonical view, the BBB can be highly dynamic, with rapid, local moments of increased permeability. These ‘Plume Events’ can be driven by behavioral events and optogenetic activation of Ventral Tegmental Area (VTA) Axons. The circuit mechanisms underlying these newly-discovered Plume Events are unknown. Rapid EC Calcium Events (ECCE) are a strong candidate driver, as increased EC Calcium (Ca2+) enhances BBB permeability ex vivo, and recent studies show rapid, discrete EC Ca2+ events in anesthetized mouse Neocortex. My Preliminary Data support this Hypothesis: Optogenetic drive of VTA Axons evokes ECCE in Neocortical vessels within 1-2s. I have also found that chemogenetically driving Chloride (Cl-) channels, known to increase EC Ca2+, can ‘open’ the BBB. Here, I systematically test three closely-related Hypotheses. In Aim I, I test the prediction that VTA Axon activity, endogenous and optogenetically-driven, evoke ECCE; In Aim II, I test the prediction that ECCE predict Plume Events; and, in Aim III, I test the prediction that externally activating EC Cl- channels can drive both BBB permeability and ECCE. I will employ 2-Photon imaging in awake mice under multiple behavioral contexts, and cellular control tools co-developed in our lab. All studies will be conducted in the Primary Somatosensory ‘Barrel’ Neocortex (SI), a key neurovascular and behavioral model system. Even if my predictions are not supported, these data should provide unique insights and may have clinical relevance (e.g., to targeted opening of the BBB). My mentor Dr. Christopher Moore has extensive experience with all of these methods. Further, Dr. Moore’s track record of expertise in exactly my desired research domain, and history of excellent mentorship results, make me confident that I am well-positioned to thrive during graduate work. My co-Mentor Dr. Diane Lipscombe is an ideal complement, as she is a leading expert in Ca2+ channel structure and function, and in linking these variables to behavior. Their collective expertise, coupled with the Brown Neuroscience Department’s classes, technical and pedagogical resources, and supportive culture, will ensure I have the mentorship and support necessary to thrive. I will broaden my graduate learning experience through taking high-level classes, attending frequent talks from a wide range of leading neuroscience researchers, and engaging with a robust peer network. Most importantly, performing my Specific Aims within this training environment will provide ideal training for reaching my long-term research goals.
