Oxytocin Modulation of Neural Circuit Function and Behavior - Revision - 3

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Project Summary Oxytocin is a peptide hormone synthesized and released from the hypothalamus for reproduction and maternal behavior. Recent studies have tagged oxytocin as a “trust” hormone, promising to improve social deficits in various mental disorders, such as autism. Despite the enthusiasm for oxytocin, contradictory results in the efficacy of oxytocin in improving human social behaviors have been reported. Such inconsistency in literature is likely due to our poor understanding of complexity of oxytocin action, which likely varies with behavioral state, experience and brain structures. We believe that a better understanding of the endogenous action of oxytocin is the key to unleash the therapeutic potential of this highly evolutionary conserved neuropeptide. Advancing our understanding requires cross-level and comparative inter-disciplinary studies by an group of investigators with overlapping interests and the technical capability to analyze oxytocin signaling across molecular, physiological, systems behavioral and levels. This includes multi-animal interactions, as many mental disorders are impactful on social behavior, over the lifespan and throughout the brain. Oxytocin action in maternal brain is especially important as it represents the most ancient and important function of oxytocin under a social context. Here we will address this critical knowledge gap. Recently, we generated the first specific antibodies to the mouse oxytocin receptor, used these antibodies to determine where these receptors are localized, and examined how oxytocin can enable pup retrieval behavior in maternal mice. Those previous studies provide a robust foundation for the current Project, in which our team aims to understand which target neural circuits are modulated by oxytocin, and if there are behavioral episodes that might be sensitive to oxytocin modulation during brief periods of social interaction. The central hypothesis is that oxytocin is absolutely necessary to initiate maternal behaviors in key areas including auditory cortex and hippocampus, but may be dispensable in experienced mothers. We will perform behavioral, optogenetic, and circuit mapping studies in adult mice to determine where and when oxytocin modulates neural circuits to enhance social information processing and subsequently improve maternal behavior. In Aim 1 we will build a new behavioral recording system to continuously monitor social interactions for days to weeks. In Aim 2, we profile oxytocin projections and oxytocin receptor expression throughout the entire adult brain to find potential hotspots of modulation. Finally in Aims 3 and 4, we perform optogenetic loss-of-function and gain-of-function type experiments to determine where and when oxytocin modulation is needed for maternal behavior or at what points might additional oxytocin release accelerate maternal behavior onset or improve steady-state performance.