Abstract
The fruit fly can evaluate its energy state and decide whether to pursue food-related cues. Here, we reveal that the mushroom body (MB) integrates hunger and satiety signals to control food-seeking behavior. We have discovered five pathways in the MB essential for hungry flies to locate and approach food. Blocking the MB-intrinsic Kenyon cells (KCs) and the MB output neurons (MBONs) in these pathways impairs food-seeking behavior. Starvation bi-directionally modulates MBON responses to a food odor, suggesting that hunger and satiety controls occur at the KC-to-MBON synapses. These controls are mediated by six types of dopaminergic neurons (DANs). By manipulating these DANs, we could inhibit food-seeking behavior in hungry flies or promote food seeking in fed flies. Finally, we show that the DANs potentially receive multiple inputs of hunger and satiety signals. This work demonstrates an information-rich central circuit in the fly brain that controls hunger-driven food-seeking behavior.
Highlights
Searching for food is costly with respect to energy and physical risk
Ghrelin, neuropeptide Y (NPY), and cholecystokinin that are secreted by these organs serve as hunger and satiety signals in the nervous system and control how an animal responds to food cues (Kairupan et al, 2016; Porte et al, 2002; Sternson et al, 2013; Sternson and Eiselt, 2017)
We found that orco and Ir8a mutant flies could not locate yeast drops (Figure 1B), indicating that flies relied on their sense of smell to find the target
Summary
Searching for food is costly with respect to energy and physical risk. Most animals are equipped with an ability to evaluate their internal energy state and use it to decide whether to respond to foodrelated cues such as taste and smell. The main nutrientand energy-sensing organs in vertebrates are stomach, gut, and white adipose tissue (Kairupan et al, 2016; Porte et al, 2002; Small and Bloom, 2004). Hormones such as leptin, ghrelin, neuropeptide Y (NPY), and cholecystokinin that are secreted by these organs serve as hunger and satiety signals in the nervous system and control how an animal responds to food cues (Kairupan et al, 2016; Porte et al, 2002; Sternson et al, 2013; Sternson and Eiselt, 2017). The detailed molecular and cellular mechanisms involved in this process remains to be elucidated
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