Regulation of aversion to noxious food by Drosophila neuropeptide Y- and insulin-like systems.

Omnivores, including humans, have an inborn tendency to avoid noxious or unfamiliar foods. Such defensive foraging behaviors are modifiable, however, in response to physiological needs. Here we describe a method for assessing risk-sensitive food acquisition in Drosophila melanogaster. Food-deprived fly larvae become more likely to feed on noxious foods (adulterated with quinine) as the duration of deprivation increases. The neuropeptide F receptor NPFR1, a mammalian neuropeptide Y (NPY) receptor homolog, centrally regulates the response to noxious food in D. melanogaster. Overexpression of NPFR1 was sufficient to cause nondeprived larvae to more readily take in noxious food, whereas loss of NPFR1 signaling led to the opposite phenotype. Moreover, NPFR1 neuronal activity may be directly regulated by the insulin-like signaling pathway. Upregulation of insulin-like receptor signaling in NPFR1 cells suppressed the feeding response to noxious food. Our results suggest that the coordinated activities of the conserved NPY- and insulin-like receptor signaling systems are essential for the dynamic regulation of noxious food intake according to the animal's energy state.