Neural Circuitry Mechanisms Underlying Maladaptive Reward Memories in Drosophila

PROJECT SUMMARY: Alcohol addiction constitutes one of the most serious public health problems worldwide. According to the CDC, the total economic cost of excessive alcohol use is estimated to be $249 billion. Despite its devastating impact, there are few effective treatments. Neural circuit based approaches to treat addiction provide a powerful

opportunity to develop more specific and effective treatments. However, circuit complexity is a significant obstacle to a comprehensive understanding of the mechanisms by which memory circuits are altered to create enduring preferences for alcohol associated cues. The current proposal will take place at Bryant University, a

primarily undergraduate institution, and will capitalize on the genetic tractability of Drosophila melanogaster and precise neurogenetic tools available to interrogate how identified memory circuits are altered by alcohol and why alcohol associated memories are so resistant to change. Although only 100,000 neurons comprise the central

nervous system of Drosophila, the neural circuitry underlying reward and addiction is remarkably complex and similar to mammals. Like mammals, Drosophila show robust preference for cues associated with alcohol intoxication that persist in the face of aversive consequences. Studies proposed here will capitalize on

established and newly developed neurogenetic tools that allow for the precise manipulation of individual neurons and visualization of circuit activity. Doing so will enable us to test the hypothesis that alcohol disrupts memory circuit activity and drives maladaptive reward seeking by engaging significantly more dopamine neurons during

acquisition. Specifically, we will use a combination of optogenetics, thermogenetics, and two-photon microscopy to capture the precise changes in dopamine neural dynamics while Drosophila learn to associate odor cues with alcohol intoxication. Additionally, we will determine if alcohol-independent activation of dopamine neurons is

sufficient to induce maladaptive memories for natural rewards. Finally, we will investigate the role of recently identified downstream regions of the fan-shaped body in modulating alcohol reward memories to understand the stability and persistence of these memories. We expect that extracellular dopamine levels and number of

recruited dopamine neurons will significantly increase across alcohol exposures and this increase is sufficient to drive maladaptive reward seeking behavior. Further, we predict that downstream convergent regions play a critical role in behavioral flexibility and disruption to these functional connections results in memories that lack

flexibility and drive maladaptive reward seeking. Ultimately, understanding general circuitry principles described first in Drosophila will provide insight to how alcohol co-opts mammalian circuits to create enduring preference for alcohol and drive maladaptive choice. An AREA grant is essential to continue our efforts in exposing

students to hands-on meritorious research, providing superior research experiences, and strengthening the research environment at Bryant University, thereby enabling more students to participate.