Loss of Neuropeptide F (NPF) Signaling Reduces the Strength of Circadian Rest-Activity Rhythms but not Feeding-Fasting Rhythms

The circadian system governs crucial physiological and behavioral processes, dictating activities like movement, hormone release, and sleep patterns over a 24-hour cycle. Disruptions to these rhythms can lead to various health problems, including cardiometabolic dysfunction. Research has demonstrated the presence of circadian rhythms of feeding behavior in diverse organisms, but the specific molecules involved are not yet identified. Neuropeptide Y (NPY) influences metabolic activity in mammals, and its counterpart, NPF, affects locomotor activity and feeding in Drosophila melanogaster. Our study aims to investigate whether NPF, its receptor (NPFR), and NPF-expressing cells play a role in regulating circadian rest-activity and feeding-fasting rhythms. We use behavioral analysis tools, such as the Drosophila Activity Monitor (DAM) and Fly Liquid-Food Interaction Counter (FLIC) systems, to study locomotor activity and feeding behavior in mutant, cellular ablation, and control flies. Our results indicate that flies lacking functional NPF or NPFR exhibit abnormal rhythms in locomotor activity behavior but not feeding behavior, suggesting a differential disruption in circadian regulation. However, when NPF-expressing cells are ablated in the brain, we observe normal locomotor activity and feeding rhythms, implying that the ablated cells are not involved in regulating the rhythmicity of these behaviors. Understanding these mechanisms will not only shed light on circadian biology in fruit flies but also have implications for addressing circadian rhythm-related health issues in humans.