Molecular and circuit mechanisms of low dose ethanol preference in Drosophila

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Project Summary/Abstract Ethanol inebriation alters the brain, inducing short-term physiological and pathological changes including ethanol tolerance, preference, and reward. These alterations are a foundation for ethanol’s longer-term effects including continued drinking in the face of negative consequences, dysphoria, and relapse. The molecular pathways co-opted by acute inebriation appear complex, and are not understood well enough to construct satisfying models of ethanol’s action. The molecular targets and neural responses for low dose ethanol remain even less well studied. In mammals, less than 10 mM ethanol internal concentration impacts the function of many neuronal molecules, and causes changes in behavior such as improved mood, decreased anxiety, and changes in cognitive functioning. The breadth of behavioral effects implies a similarly broad engagement of neural circuitry for emotion, motivation, and cognition. Low internal concentrations of ethanol in the fruit fly Drosophila increase locomotor activity, induce ethanol preference and ethanol reward, and are achieved in 2-choice preference assays. We discovered an epigenetic pathway impacted by acute ethanol intake that regulates the availability of key presynaptic molecules, and that is required for both ethanol preference and reward. This pathway functions in the mushroom bodies that are critical for learning, memory, and assigning positive and negative valence. We hypothesize that low dose ethanol causes maladaptive learning to occur in the Drosophila mushroom body reward/association circuitry through molecular and neural activity mechanisms, leading to a shift from ethanol aversion to preference. We propose to determine the functionally relevant molecular changes induced by low dose ethanol specifically in the Drosophila mushroom bodies, and how low dose ethanol preference development affects mushroom body functional circuit properties. We will test for the relationship of ethanol’s impact on the circuit with sugar reward memory that requires the same mushroom body neurons. Our long term goals are to integrate how low dose ethanol’s molecular effects impact circuit configuration to cause lasting behavioral change, and how ethanol differs from the processing of natural, high valence stimuli in the same circuit.