Drosophila melanogaster as a model to study drug addiction

Abstract

Animal studies have been instrumental in providing knowledge about the molecular and neural mechanisms underlying drug addiction. Recently, the fruit fly Drosophila melanogaster has become a valuable system to model not only the acute stimulating and sedating effects of drugs but also their more complex rewarding properties. In this review, we describe the advantages of using the fly to study drug-related behavior, provide a brief overview of the behavioral assays used, and review the molecular mechanisms and neural circuits underlying drug-induced behavior in flies. Many of these mechanisms have been validated in mammals, suggesting that the fly is a useful model to understand the mechanisms underlying addiction.

Fig. 1

Common genetic tools in Drosophila. a The Gal4/UAS system (Brand and Perrimon 1993). The transcriptional activator Gal4 is expressed in a spatially restricted pattern and activates any gene placed downstream of the upstream activating sequence (UAS). b The TARGET system (McGuire et al. 2003). At the restrictive temperature (30°C), Gal80^ts is inactive, Gal4 is active and UAS-driven genes are expressed. At the permissive temperature (19°C), Gal80^ts is active, Gal4 is inhibited, and UAS-driven genes are not expressed. c The Shibire^ts system (Kitamoto 2001). At the restrictive temperature (30°C), but not the permissive temperature (19°C), Shi^ts blocks neurotransmission by disrupting endocytosis and thereby depleting synaptic vesicles. d The TrpA1 system (Hamada et al. ; Pulver et al. 2009). At the restrictive temperature (27°C), but not the permissive temperature (19°C), cation flow through the temperature-gated cation channel dTRPA1 causes neuronal depolarization

Fig. 2

Assays to measure alcohol-induced behavior in Drosophila. a The inebriometer measures ethanol-induced loss of postural control by measuring the time required for flies to fall down the mesh baffles from the top to the bottom of the column (Weber ; Moore et al. 1998). b The booz-o-mat allows for the measurement of ethanol-induced hyperactivity and sedation while streaming vaporized ethanol into horizontal tubes containing groups of flies. Hyperactivity is measured by filming the flies and using tracking software to calculate their locomotor speed. Sedation is measured by recording the time required for flies to exhibit the loss-of-righting reflex (Wolf et al. 2002). c The two-choice CAFE assay measures consumption preference for food containing ethanol compared to normal food (Ja et al. ; Devineni and Heberlein 2009). d Conditioned ethanol preference is measured by training the flies in a sealed container to associate a neutral odor with the presence of an intoxicating dose of ethanol, and later testing preference for that odor in the absence of ethanol using a Y-maze (Kaun et al. 2011)