A subset of octopaminergic neurons that promotes feeding initiation in Drosophila melanogaster

Author(s): Youn, Hyesoo | Advisor(s): Scott, Kristin | Abstract: In order for animals to achieve metabolic hometostasis and maintain fitness, it iscrucial for them to make appropriate feeding decisions and precisely execute feedingbehaviors. Animals make feeding decisions based on various factors including theirphysiological needs and palatability of the food source. Despite of their importance,neural and molecular mechanisms underpinning the integration of these internal andexternal information have yet to be fully elucidated. In addition, octopamine, anequivalent of mammalian norepinephrine, has been suggested to regulate feedingbehavioral responses in invertebrates. However, how octopamine modulates feedingbehavior has been unclear. Utilizing Drosophila melanogaster as a model system, Isought to examine the neural and molecular mechanisms underlying octopaminergicfeeding modulation in this thesis.In specific, I investigated the role of a subset of octopaminergic neurons, theOA-VPM4 cluster, in sucrose acceptance behavior. Thermogenetic activation of Gal4lines containing OA-VPM4 promoted proboscis extension to sucrose, while optogeneticinactivation reduced extension. Anatomically, the presynaptic terminals of OA-VPM4are in close proximity to the presynaptic terminals of sugar-responsive gustatorysensory neurons. Moreover, RNAi knockdown of a specific class of octopaminereceptor, OAMB, selectively in sugar-sensing gustatory neurons decreased thebehavioral response to sucrose. By calcium imaging experiments, I found thatapplication of octopamine potentiates sensory responses to sucrose in satiated flies.Preliminary results from the experiments investigating functional connectivitybetween sensory neurons and OA-VPM4 suggest that OA-VPM4 is likely anupstream modulator of the sensory neurons. Taken together, these findings suggest amodel by which OA-VPM4 promotes feeding behavior by modulating the activity ofsensory neurons.