Serotonin regulates nutrient-dependent food intake in Drosophila.

Serotonin is a key neurotransmitter in feeding behavior. However, its role in regulating food intake based on nutrient composition remains unclear. In this study, we utilized the Drosophila model to investigate the influence of serotonin on feeding behavior. By employing transient thermogenetic tools, we transiently manipulated the activity of serotonergic neurons while minimizing effects on other physiological processes, including sleep. By measuring the intake of sucrose, sucralose, yeast, and tryptone, we evaluated the role of serotonin signaling in nutrient-dependent food intake. Our findings demonstrate that distinct subsets of serotonergic neurons in the subesophageal zone (SEZ) independently regulate the intake of sucrose and protein. Additionally, we identified serotonin receptors 5-HT2B and 5-HT1A in the mushroom body γ lobes as key modulators of sucrose and protein consumption, respectively. Taken together, our results highlight the role of serotonin in nutrient-specific feeding regulation and provide insights into the neural mechanisms underlying dietary choices.