Protein Hunger is Encoded by Branch-specific Plasticity of a Dedicated Dopamine Circuit

Abstract

In an unpredictable environment with varied food sources, animals must appropriately regulate the amount and type of food they consume. Indeed, hunger, a motivational state representing the physiological need for food, is not a unitary phenomenon, but rather can exist individually for specific nutrients, such as salt or protein. The shifting of food preference driven by nutrient-specific hunger can be essential for survival1, yet little is known about the mechanisms underlying this process. Here, we identify a small subset of dopaminergic neurons that mediate protein-specific hunger in Drosophila. These neurons are both necessary and sufficient for the homeostatic drive to consume protein. The activity of these neurons is increased following protein deprivation. Activation of these neurons not only promote protein intake, but also restrict sugar consumption, and perform both functions by signaling to distinct downstream neurons via discrete terminal branches. Remarkably, protein deprivation triggers plastic changes in the protein-specific, but not sugar-specific, branch of these dopaminergic neurons, thus enabling selective and sustained consumption of protein.