Hunger states modulate aggression via opposing dopamine pathways.

Hunger drives aggression, making animals "hangry". Yet the underlying neural mechanism is unclear. Here, we identified a "hangry neuron" in the mushroom body of Drosophila that transforms hunger states into aggression intensity. This transformation is graded and nutrient-specific, precisely coupling internal needs to aggressive actions. Dopaminergic inputs to the hangry neuron play a critical role in this process by conveying the information about hunger states, and by bidirectionally modulating hangry neuron's excitability via Dop1R1 and Dop1R2 receptors, which activate intracellular cAMP and calcium pathways, respectively, thereby oppositely modulating excitability. Together, our study reveals the unexpected function of the mushroom body - traditionally viewed as the learning and memory center in Drosophila - in modulating aggression, and identifies a simple circuit design in this species whereby a single neuron integrates distinct dopamine signaling pathways to mediate flexible behavior, a function that is typically implemented by the basal ganglia system in mammals.