Toddes, Carlee2022-08-292022-08-292022-05https://hdl.handle.net/11299/241329University of Minnesota Ph.D. dissertation. May 2022. Major: Neuroscience. Advisors: Patrick Rothwell, Robert Meisel. 1 computer file (PDF); x, 145 pages.Social interaction is a fundamental behavior necessary for the survival of every animal species on earth. These interactions encompass a complex range of behaviors that require coordinated activity of multiple neural circuits for successful expression. While these behaviors have been the focus of intense neuroscientific studies for the last several decades, there remains a dearth of knowledge regarding the specific cells and receptor subsystems that lead to their expression or disruption. This dissertation focuses specifically on uncovering the role of the endogenous opioid system, namely mu opioid receptors, on affiliative social interaction in mice. Since affiliative social interaction encompasses a broad range of social behaviors dependent upon a series of interconnected neural circuits, the first series of experiments were designed to elucidate which swath of behaviors the mu opioid system specifically regulates and pinpoint a neural hub upon which they act. Following the identification of reciprocal interactions as the main behavior modulated by mu opioid receptor expression and the identification of the nucleus accumbens as a key site of cellular reorganization, the second series of experiments were designed to identify specific cellular elements within the nucleus accumbens that modulate reciprocal social interactions.enNucleus AccumbensOpioidSocial BehaviorThesis or Dissertation