The fly liquid-food electroshock assay (FLEA) suggests opposite roles for neuropeptide F in avoidance of bitterness and shock

Abstract

Background Proper regulation of feeding is important for an organism’s well-being and survival and involves a motivational component directing the search for food. Dissecting the molecular and neural mechanisms of motivated feeding behavior requires assays that allow quantification of both motivation and food intake. Measurements of motivated behavior usually involve assessing physical effort or overcoming an aversive stimulus. Food intake in Drosophila can be determined in a number of ways, including by measuring the time a fly’s proboscis interacts with a food source associated with an electrical current in the fly liquid-food interaction counter (FLIC). Here, we show that electrical current flowing through flies during this interaction is aversive, and we describe a modified assay to measure motivation in Drosophila. Results Food intake is reduced during the interaction with FLIC when the electrical current is turned on, which provides a confounding variable in studies of motivated behavior. Based on the FLIC, we engineer a novel assay, the fly liquid-food electroshock assay (FLEA), which allows for current adjustments for each feeding well. Using the FLEA, we show that both external incentives and internal motivational state can serve as drivers for flies to overcome higher current (electric shock) to obtain superior food. Unlike similar assays in which bitterness is the aversive stimulus for the fly to overcome, we show that current perception is not discounted as flies become more food-deprived. Finally, we use genetically manipulated flies to show that neuropeptide F, an orthologue of mammalian NPY previously implicated in regulation of feeding motivation, is required for sensory processing of electrical current. Conclusion The FLEA is therefore a novel assay to accurately measure incentive motivation in Drosophila. Using the FLEA, we also show that neuropeptide F is required for proper perception or processing of an electroshock, a novel function for this neuropeptide involved in the processing of external and internal stimuli.

The Stage-Based Model of Addiction—Using Drosophila to Investigate Alcohol and Psychostimulant Responses

“…The link between GPM6B and impulsivity opens a door of opportunity for researchers to begin understanding the molecular mechanisms of impulsivity, especially because GPM6B has an ortholog in the fly, M6 . One can investigate the mechanism of M6 by manipulating this gene in flies and observing how M6 -manipulated flies behave in impulsivity assays, like the fly liquid–food electroshock assay (FLEA) [ 141 ]. The FLEA is a two-choice assay similar to the FLIC ( Figure 2 ) that incorporates an electric shock as a variable.…”

The Use of Drosophila to Understand Psychostimulant Responses

“…In the context of addiction, several newer assays of consumption and preference such as the Fly Liquid-Food Interaction Counter [ 200 ] and Fly Liquid-Food Electroshock Assay (FLEA) [ 201 ] provide improvements in automation for acquisition as well as analysis of behavior, enabling comprehensive tracking of experience dependent changes in response. Both the FLIC and the FLEA support high-throughput continuous monitoring of behaviors indicative of consumption and preference.…”

CRUMB: a shiny-based app to analyze rhythmic feeding in Drosophila using the FLIC system

“…22 Since then, several other groups have adopted the system and used it to address different biological questions including rhythmic feeding and metabolic homeostasis. 18,[23][24][25][26][27][28][29][30][31][32] Available options of software to analyze locomotor activity from DAMS have multiplied over the years, offering different user interphases and developed in different coding languages [33][34][35][36][37] (summarized in Cai et al 15 ). In contrast, due to its recent implementation, user-friendly tools to analyze FLIC data are still scarce, 23 and available scripts require the user to understand and use R coding syntax.…”

“…18,[23][24][25][26][27][28][29][30][31][32] Available options of software to analyze locomotor activity from DAMS have multiplied over the years, offering different user interphases and developed in different coding languages [33][34][35][36][37] (summarized in Cai et al 15 ). In contrast, due to its recent implementation, user-friendly tools to analyze FLIC data are still scarce, 23 and available scripts require the user to understand and use R coding syntax. Here we present CRUMB (Circadian Rhythm Using Mealtime Behavior), a shiny app based on the popular DAMS Shiny app Shiny-R DAM combined with the core FLIC code master scripts provided with the equipment (GitHub FLIC R code).…”