Beyond Eating Behavior: Decoding the Role of Central Extended Amygdala PKC-delta Neurons in Energy Balance and Activity-Based Anorexia

Abstract

Anorexia nervosa (AN) is a psychiatric disease characterized by abnormal eating behavior, self-starvation, intense fear of weight gain, and is often associated with excessive exercise. Despite extensive research, significant gaps persist in elucidating the precise neural mechanisms underlying development of AN. This dissertation addresses this gap by focusing on the role of protein kinase-C delta (PKC-) neurons within the central extended amygdala (EAc) in the development of activity-based anorexia (ABA), a common animal model for AN. Through a series of experiments employing multidisciplinary approaches, including behavioral assays, genetically-targeted manipulation, in vivo calcium imaging, neuronal tracing, and immunohistology, this dissertation reveals involvement of EAcPKC- neurons in ABA development and associated behaviors. Ablation of PKC- neurons in two nuclei of the EAc, the central amygdala nucleus (CeA) and bed nucleus of the stria terminals (BNST), in mice prevents the development of ABA, suggesting a critical role in the pathological progression of AN. Importantly, simultaneous ablation of PKC- neurons in both nuclei are required for consistent prevention, implying synergistic or additive dynamics for their function in regulating ABA. Furthermore, while presentation of food is associated with increased activity of these neurons as mice develop ABA, indicating a role in modulating the disrupted eating behavior phenotype, acutely silencing their activity with chemogenetic methods does not impede development of ABA or mitigate any phenotypes, suggesting a more nuanced mechanism. Additional experiments reveal other functions of EAcPKC- neurons in energy balance, beyond their previously established role in eating behavior and anorexigenic (i.e., appetite suppressing) signaling, shedding light on their potential contribution to modulating other metabolic behaviors. Specifically, acute activation of CeAPKC- increases locomotor behavior, demonstrating a role in energy expenditure. Furthermore, the ABA experiments and results from immunohistochemistry investigation point to a potential link between EAcPKC- neurons and circadian-based eating behavior. Ultimately, the findings in this dissertation not only deepen our understanding of AN’s neural circuit basis but also offer insights into novel functions of EAcPKC- neurons in energy homeostasis and mechanisms as to how they regulate phenotypical behaviors associated with AN, opening avenues for further exploration in the field of both ABA and EAc neural circuitry.