The Role of Dopamine in Operant Learning and Memory

Dopamine is a neurotransmitter that regulates many physiological processes including reward, motivation, movement, learning and memory, and reinforcement. The cognitive processes in which one associates a specific action or behavior with a positive or negative consequence is referred to as operant learning, and is a robust occurrence in everyday life. It is also believed to play a significant role in the development of drug addiction and has been shown that increased levels of dopamine are associated with the intake of addictive drugs such as cocaine and alcohol; however, the underlying cellular mechanisms of this learned behavior are not well understood. By using Drosophila melanogaster as a model system, we can genetically manipulate and dissect the mechanisms underlying operant learning and memory. Because these complex biological processes are evolutionarily conserved, the data obtained here can be related to the behavioral plasticity observed in vertebrates. In a conditioned courtship assay, a male fly\u27s courtship behavior is influenced by persistent rejection of a mated female. The male fly learns to associate unsuccessful courtship and copulation with the female fly and displays a generalized aversion (via courtship suppression) toward a virgin female. The goal of this study is to elucidate dopamine\u27s roles in this operant conditioning. For this task, we have tested flies lacking D1 receptor dDA1 (dumb), D2 receptor dDR2 (dd2r), or dopamine transporter DAT (fmn, fmnZuker). Once we identify important components mediating operant learning and memory, their functional sites (brain structures) and underlying cellular mechanisms will be clarified. Knowledge obtained in this study should shed light onto the complex and multifaceted pathways in which learning through association occurs