Increased dopamine induces lethal foraging in Drosophila. Wanhao Chi, Cristi Frazier, Liwen Xu, Jeff Beeler, Xiaoxi Zhuang. Neurobiology, University of Chicago,IL.

   Foraging strategies reflect economic decision-making. When food is scarce, it is essential for survival to balance the energy gained from potential food acquisition against the energetic cost of finding food. The effectiveness of different strategies, such as exploiting a food source versus expending energy on exploration, will be dependent on food availability in the environment. Despite an abundance of studies on neural circuits encoding value and economic decision-making, and the significance of such studies is based on the assumption that neural mechanisms underlying adaptive economic choice ultimately promote survival. However, studies rarely tested this most fundamental aspect of neuroeconomics directly. Dopamine is implicated in reward and economic decisions. Our recent study in mice reported that elevated dopamine via reduced dopamine transporter (DAT) reduced coupling between reward history and action choice. As a consequence, mutant mice expressed diminished exploitation of readily available food, increased energy expenditure unrelated to procurement of food and impaired energetic thriftiness. In order to test if such a phenotype can affect survival when food source is limited, we turned to Drosophila. The fumin mutant has a truncated DAT protein and severely reduced dopamine reuptake. We set up a foraging paradigm, in which a thin capillary is the sole food source inside a cylinder compartment. Compared to wild-types, activities of fumin flies were much less directed toward food, and their consumption and survival severely impaired. Such a phenotype can be rescued genetically by re-expressing DAT. Dopamine may play a critical role in modulating the balance between exploration and exploitation. Higher dopaminergic activity promotes exploration at the expense of energetic thrift, decreasing foraging efficiency and survival when food source is limited.