Pre- and Postsynaptic Role of Dopamine D2 Receptor DD2R in Drosophila Olfactory Associative Learning.

Cheng Qi,Daewoo Lee

doi:10.3390/biology3040831

Abstract

Dopaminergic neurons in Drosophila play critical roles in diverse brain functions such as motor control, arousal, learning, and memory. Using genetic and behavioral approaches, it has been firmly established that proper dopamine signaling is required for olfactory classical conditioning (e.g., aversive and appetitive learning). Dopamine mediates its functions through interaction with its receptors. There are two different types of dopamine receptors in Drosophila: D1-like (dDA1, DAMB) and D2-like receptors (DD2R). Currently, no study has attempted to characterize the role of DD2R in Drosophila learning and memory. Using a DD2R-RNAi transgenic line, we have examined the role of DD2R, expressed in dopamine neurons (i.e., the presynaptic DD2R autoreceptor), in larval olfactory learning. The function of postsynaptic DD2R expressed in mushroom body (MB) was also studied as MB is the center for Drosophila learning, with a function analogous to that of the mammalian hippocampus. Our results showed that suppression of presynaptic DD2R autoreceptors impairs both appetitive and aversive learning. Similarly, postsynaptic DD2R in MB neurons appears to be involved in both appetitive and aversive learning. The data confirm, for the first time, that DD2R plays an important role in Drosophila olfactory learning.

Highlights

Dopamine (DA) is an important neurotransmitter mediating a variety of brain functions including locomotion, reward, awareness, learning and memory, and cognition [1,2,3]
Our results showed that suppression of presynaptic DD2R autoreceptors impairs both appetitive and aversive learning
Our results showed that both presynaptic DD2R autoreceptors and postsynaptic receptors are required for aversive and appetitive olfactory learning in Drosophila larvae

Summary

Introduction

Dopamine (DA) is an important neurotransmitter mediating a variety of brain functions including locomotion, reward, awareness, learning and memory, and cognition [1,2,3]. Genetic and pharmacological studies revealed that the dopaminergic system in the fruit fly Drosophila melanogaster plays multiple roles in motor function and associative learning [3,4]. Using the sophisticated genetic tools available for the fruit fly, it has been firmly established that release of dopamine is required for associative learning in Drosophila adults and larvae [5,6,7,8]. Dopaminergic neural circuits mediating olfactory learning have been characterized in the fruit fly brain [9,10]. DA receptors can be divided into two families in vertebrates [2]

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Conclusion