Feeding decision-making by a single neuron via disparate neurotransmitters.

Animals use gustatory information to decide whether to ingest nutritious substances or avoid toxic ones. Although certain neurons in the gustatory circuits respond to both aversive and appetitive signals, how these neurons resolve inputs with opposing valences is unknown. Here, we examine how the Drosophila melanogaster neuropeptide leucokinin (LK) affects gustatory information processing to elicit the appropriate feeding behaviors. We identify the subesophageal LK neurons (SELKs) as downstream synaptic partners of gustatory receptor neurons and show that these two groups are functionally connected. We then show that SELKs affect bitter avoidance through LK release and food intake in an acetylcholine-dependent manner. Our study uncovers a mechanism whereby strong activation of SELKs results in LK release, leading to feeding suppression, while weak activation results in acetylcholine-dependent feeding promotion. Thus, our results reveal that a single pair of neurons, SELKs, differentially controls opposing feeding behaviors via distinct neurotransmitters.