Feeding Behavior and Lipid Content Depend on Dopamine Level in Drosophila melanogaster

Dopamine is well known to contribute to regulating a wide range of vital functions in various animal taxa, playing an evolutionarily conserved role of a neurohormone and neurotransmitter. Feeding is one of the functions. Its regulation by dopamine in mammals has been demonstrated many times. However, data on the dopamine regulation of feeding in insects are scarce. Dopamine is synthesized from 3,4-dihydroxy-L-phenylalanine (L-DOPA), and the addition of L-DOPA to diet sharply increases the dopamine levels in insects. In this study, L-DOPA administered with food was tested for effects on the food intake, total lipid content, and body weight in the fruit fly Drosophila melanogaster. The effects on the parameters were found to be divergent. Higher dopamine levels increased the food intake, but simultaneously decreased the body weight and total lipid content in D. melanogaster adults. Based on the findings, dopamine was concluded to play an important role in regulating both feeding behavior and carbohydrate and fat metabolism in insects, the two regulatory mechanisms being independent of each other.