Absolute ethanol intake drives ethanol preference in Drosophila

TL;DR

This study investigates how ethanol preference in Drosophila is influenced by absolute ethanol intake and overall food consumption, highlighting the role of diet composition and intake levels in ethanol preference.

Contribution

It demonstrates that ethanol preference depends on absolute ethanol intake and total food volume, not just caloric content, clarifying factors influencing ethanol preference in flies.

Findings

Ethanol preference is abolished on high nutrient diets.

Manipulating food intake alters ethanol preference.

Absolute ethanol intake predicts preference better than caloric content.

Abstract

Factors that mediate ethanol preference in Drosophila melanogaster are not well understood. A major confound has been the use of diverse methods to estimate ethanol consumption. We measured fly consumptive ethanol preference on base diets varying in nutrients, taste, and ethanol concentration. Both sexes showed ethanol preference that was abolished on high nutrient concentration diets. Additionally, manipulating total food intake without altering the nutritive value of the base diet or the ethanol concentration was sufficient to evoke or eliminate ethanol preference. Absolute ethanol intake and food volume consumed were stronger predictors of ethanol preference than caloric intake or the dietary caloric content. Our findings suggest that the effect of the base diet on ethanol preference is largely mediated by total consumption associated with the delivery medium, which ultimately determines the level of ethanol intake. We speculate that a physiologically relevant threshold for ethanol intake is essential for preferential ethanol consumption.