Dissection of theDrosophilaneuropeptide F circuit using a high-throughput two-choice assay

Abstract

In their classic experiments, Olds and Milner showed that rats learn to lever press to receive an electric stimulus in specific brain regions. This led to the identification of mammalian reward centers. Our interest in defining the neuronal substrates of reward perception in the fruit fly Drosophila melanogaster prompted us to develop a simpler experimental approach wherein flies could implement behavior that induces self-stimulation of specific neurons in their brains. The high-throughput assay employs optogenetic activation of neurons when the fly occupies a specific area of a behavioral chamber, and the flies' preferential occupation of this area reflects their choosing to experience optogenetic stimulation. Flies in which neuropeptide F (NPF) neurons are activated display preference for the illuminated side of the chamber. We show that optogenetic activation of NPF neuron is rewarding in olfactory conditioning experiments and that the preference for NPF neuron activation is dependent on NPF signaling. Finally, we identify a small subset of NPF-expressing neurons located in the dorsomedial posterior brain that are sufficient to elicit preference in our assay. This assay provides the means for carrying out unbiased screens to map reward neurons in flies.reward circuit | high-throughput two-choice assay | optogenetics | neuropeptide F | Drosophila

PiVR: an affordable and versatile closed-loop platform to study unrestrained sensorimotor behavior

“…Consequently, activating light-gated ion channels expressed in the sensory neurons of adult flies requires higher light intensities than in semi-transparent larvae (8,22). The background illumination system of PiVR was modified to deliver light intensities as high as 50 µW/mm 2 to penetrate the adult-fly cuticle (37). Despite a tenfold increase in locomotion speed between adult flies and larvae (peak speed of 12 mm/s and 1.6 mm/s, respectively), PiVR accurately monitored the motion of adult fruit flies for the entire duration of 5-min trials ( Figure 3A-B).…”

“…Optogenetic activation of the Gr66a-expressing neurons alone is sufficient to elicit aversive responses (37). Using the closed-loop tracking capabilities of PiVR ( Figure 3A), we examined taste-driven responses of flies expressing the red-light-gated ion channel CsChrimson in their Gr66a-expressing neurons.…”

“…Adult flies can walk approximately one order of magnitude faster than larvae crawl (12 mm/s and 1.6 mm/s, respectively). The detection of bitter taste elicits strong aversive spatial responses in adult flies (37). PiVR can be used to present flies with virtual realities in which space is organized according to a checkerboard where quadrants elicit or not virtual bitter tastes ( Figure 3B).…”

Diverse food-sensing neurons trigger idiothetic local search in Drosophila

“…Source Identifier Unless otherwise noted, we starved flies prior to experiments by housing them for 33-42 hours in a vial supplied with a tissue (KimTech) containing 1 ml of distilled water with 800 µM ATR. Protein-starved flies were housed for 5 days in a vial supplied with a tissue containing 1 mL of 10% sucrose with 800 µM ATR, and then transferred for [33][34][35][36][37][38][39][40][41][42] hours to a vial supplied with a tissue containing 1 ml of distilled water with 800 µM ATR.…”

Innate visual preferences and behavioral flexibility inDrosophila

“…Behavioral choices are guided by innate preferences or 'instinct', as well as by 39 more flexible cognitive processes such as attention (VanRullen and Thorpe, 2001; Smith and 40 Gøtzsche and Woldbye, 2016). In Drosophila, an increase in dNPF levels in the brain has 82 been associated with increased aggression (Dierick and Greenspan, 2007), arousal (Chung 83 et al, 2017), and reward learning (Krashes et al, 2009;Shao et al, 2017). Further, dNPF 84 modulates olfactory learning by inhibiting DA neurons that provide positive and negative 85 valence cues to the mushroom bodies (MB) (Zhang et al, 2007;Krashes et al, 2009;Hattori 86 et al, 2017), a structure that has primarily been associated with olfactory memory (Keene 87 and Waddell, 2007).…”