Project Summary The hypothalamus is the master regulator of the neuroendocrine system, it synapses to multiple brain regions and coordinates physiological functions of the body. Magnocellular neurons (MCN) are key producers of oxytocin and vasopressin, they regulate neuroendocrine functions and differentially secrete oxytocin into the brain, the cerebrospinal fluid, and the circulatory system. How MCN differentially regulate oxytocin release remains unresolved. Oxytocin is involved in and studied as a candidate treatment for psychiatric and metabolic conditions such as autism, depression, and post-traumatic stress. Miniaturized models of organs and tissues are indispensable tools for bridging the gap between preclinical animal models and clinical trials. Human and animal microfluidic tissue-chips provide unparalleled control and access to cells and tissues where anatomical and technical barriers preclude in vivo studies. We will create a microfluidic-based brain tissue chip for coupling brain slices and primary neurospheres from at least two regions of the brain. Surface-patterned guidance cues will be used to direct the growth of axons from oxytocinergic magnocellular neurons toward target brain tissues. Our microfluidic system will allow for brain-to-synapse connections for the direct observation of nano-scale oxytocin vesicles to achieve detailed studies of how different drugs influence the locations and dynamics of oxytocin vesicle release. More generally, potential applications of our brain-to-brain tissue culture system could include the ability to connect multiple brain regions in vitro for the benefit of immune regulation studies, neuroendocrine regulation studies, neurogenesis and migration studies, and how drugs influence molecular and cellular dynamics.