Researchers have identified the neural circuit that drives protein cravings in fruit flies. Protein is an essential nutrient and thus its intake must be actively regulated. When an animal's store of protein runs low, neural circuits alert the animal to this deficiency and prompt cravings, processes that are critical for survival, yet little is known about these processes' underlying mechanisms. To explore the neurons that regulate protein appetite, Qili Liu et al. monitored the neural activity of mated female fruit flies as they were deprived of yeast, a major source of protein for this species. The team identified a subset of dopamine neurons, dubbed DA-WED cells, in the protocerebral posterior medial 2 region of the brain. When these neurons were inactivated, the flies' preference and consumption of yeast greatly declined, while general hunger, thirst, and salt appetite were not affected. In male fruit flies, activation of DA-WED neurons induced yeast preference and consumption, while inhibition had the opposite effect. Monitoring of DA-WED neurons over time revealed that they become more active as yeast deprivation progresses.
###
Science