Project Summary / Abstract A single acute ethanol exposure causes lasting changes in behavior and brain function. Acute changes may form a foundation for progressive changes with subsequent ethanol exposures, incrementally increasing the risk of alcohol use disorder. We found evidence of structural changes in presynaptic active zones in neurons that promote behavioral plasticity (tolerance, preference, and reward), in response to acute ethanol in Drosophila. In mammals there is much evidence for electrophysiological and circuit driven changes in presynaptic activity in models of AUD. However, molecular changes at presynapses remain difficult to measure, making assessment of the mechanistic coding of plasticity incomplete. Advances in Drosophila transgenics and microscopy resolution let us determine the effects of ethanol on evolutionarily conserved presynaptic architecture. We hypothesize that presynaptic changes contribute to the coding of ethanol-induced behavioral plasticity, to bias the behavioral and circuit effects of subsequent ethanol exposures. The goal of this exploratory grant proposal is to gain a mechanistic handle on ethanol-induced presynaptic change in Drosophila. The long-term goal is to develop a new approach towards understanding how alcohol changes the structure and function of the brain, that can be applied across a variety of model organisms for addiction research, and combined with rigorous physiological and circuit-level understanding. To accomplish our goal, we will perform three independent experiments. First, We will ask how widespread presynaptic plasticity is found in the seats of Drosophila learning and memory. Second, we will ask about the role of presynaptic plasticity genes in ethanol-induced presynaptic change. Third, we will ask if presynaptic change is due to a property of the circuitry upstream and downstream of the sites of change. We predict that the study outcome will define specific presynaptic sites that show ethanol-induced plasticity. This information will allow us to explore the functional role of synapse assembly and maintenance pathways, and homeostatic versus Hebbian mechanisms, taking into account the neurotransmitter and neuromodulator synaptic profiles.