Modulation of Future Feeding Behavior by Past Taste Experience in Drosophila melanogaster Restricted; Files Only

Abstract

      There are five basic tastes that can influence behavior depending on their valence, such as bitter driving aversion and sugar driving attraction. Like mammals, the fruit fly Drosophila melanogaster contains taste-specific gustatory receptor neurons (GRN) that can promote or suppress feeding depending on taste valence. Flies also contain GRNs to sense water, which is attractive to thirsty flies but only mildly attractive under non-thirsty conditions. While associative learning paradigms have been previously studied in Drosophila, an animal will frequently encounter taste stimuli sequentially rather than simultaneously in the natural environment. Thus, it becomes important to integrate taste information over time to make an optimal feeding decision. A previous study from our lab characterized a new taste modulation paradigm in which a brief sugar experience increases the future feeding response to water on a timescale of seconds to minutes. This study suggested that neurons in the sugar neural pathway act to modulate neurons in the water pathway, potentially increasing their excitability to future stimulation. Here, we sought to determine which neurons in the sugar pathway are responsible for this modulation. Using optogenetic tools, we artificially activated individual neurons in different layers of the sugar circuit and recorded changes in feeding responses to water before and after optogenetic activation. Activation of two excitatory second-order sugar neurons, Zorro and G2N-1, caused an increased water response while activation of an inhibitory second-order neuron and excitatory third- or fourth-order neurons did not cause modulation. We concluded that specific second-order neurons in the sugar neural pathway act to modulate the water pathway to increase future feeding responses. As our results begin to map out the model for the sugar modulation of water response, they have greater implications in understanding learning and memory on a short timescale. These results can further provide more insight on feeding behavior modulation in more complex organisms, such as mammals.

Table of Contents

Table of Contents

INTRODUCTION……………………………………………………………………………….1

           Background………………………………………………………………………………..1

Taste and feeding………………………………………………………………….1

                      Drosophila taste system…………………………………………………………...1

                      Taste modulation in Drosophila…………………………………………………..3

           Hypotheses/Goals…………………………………………………………………………7

MATERIALS AND METHODS………………………………………………………………12

           Optogenetics/Genetic Crosses…………………………………………………………...12

           Fly Maintenance and Collection…………………………………………………………12

           Proboscis Extension Response…………………………………………………………...13

           Quantification and Statistical Testing……………………………………………………14

RESULTS……………………………………………………………………………………….16

DISCUSSION…………………………………………………………………………………...31

REFERENCES………………………………………………………………………………….35

 

Figures and Tables

INTRODUCTION……………………………………………………………………………….1

FIGURE 1………………………………………………………………………………....3

FIGURE 2………………………………………………………………………………....6

FIGURE 3………………………………………………………………………………....7

FIGURE 4………………………………………………………………………………....9

FIGURE 5………………………………………………………………………………..10

MATERIALS AND METHODS………………………………………………………………12

           TABLE 1………………………………………………………………………………....14

RESULTS……………………………………………………………………………………….16

           FIGURE 6………………………………………………………………………………..17

           TABLE 2………………………………………………………………………………....19

FIGURE 7………………………………………………………………………………..20

FIGURE 8………………………………………………………………………………..21

FIGURE 9………………………………………………………………………………..23

FIGURE 10………………………………………………………………………………24

FIGURE 11………………………………………………………………………………27

FIGURE 12………………………………………………………………………………29

DISCUSSION…………………………………………………………………………………...31

REFERENCES………………………………………………………………………………….35

 

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Cell Biology, Neuroscience
Keyword	Neuroscience
Committee Chair / Thesis Advisor	Anita Devineni, Emory University
Committee Members	Andrea Roeser, Emory University Alan Emanuel, Emory University

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