Alcohol Increases Aggression in Flies

Abstract

Alcohol-induced aggression is a destructive and widespread phenomenon, but we understand very little about the mechanisms that produce this behavior. We found that two different alcohol exposures potentiate aggression in male flies. (1) A pharmacologically relevant dose of alcohol increases aggression and decreases a goal-directed behavior in male flies. (2) In addition, the odor of alcohol itself enhances intermale aggression by potentiating olfactory signaling by cis-vaccenyl acetate (cVa), a volatile male pheromone. Characterizing these behaviors in the genetically tractable fruit fly can lead to a better understanding of the molecular correlates that regulate alcohol-induced aggression in humans and provide insights into an ethologically relevant behavior.One Sentence Summary: We identified two pathways through which alcohol stimulates intermale aggression in flies; one acts by potentiating a male olfactory pheromone while the other is mediated by the systemic effects of alcohol.

Alcohol boosts pheromone production in male flies and makes them sexier

“…The responses to the alcohols were observed in OSN type ab1A (Or42b) with a stronger affinity to ethanol, and in ab2A (Or59b) and pb1A (Or42a) with stronger responses towards methanol. We also noted a synergy between ethanol exposure and at1A response to cVA (which has been demonstrated previously 6,20,21 ), as well as a possible synergy between at4A responses towards methanol exposure and ML ( Supplementary Figure 5d,e), although neither alcohol directly activated these trichoid associated OSNs when presented alone. At the OSN level, we did not observe any variation in SSR response based on mating status (mated vs. non-mated males) (Figure 3d).…”

“…We thus propose that this makes males more attractive for females that are seeking good genes for their progeny. Moreover, the increased attraction to alcohol by virgin males appears to give a direct advantage in subsequent courtship, as opposed to depression or substance abuse interpretations of this behavior 5,6 . However, contact with alcohols, especially methanol, is inherently dangerous, as it is toxic.…”

Neuroecology of Alcohol Preference in Drosophila

“…appear to modulate social interactions (9,10,26,70,114). Previous studies have begun to show that ethanol also modulates the sensitivity of OSNs present in these trichoid sensilla to their respective pheromone odorants, and that exposure to ethanol-rich foods increases basal firing rates and synergizes subsequent stimulation of trichoid OSNs with their best pheromone ligands (53,94,95). This increase in neuronal firing may be directly related to the olfactory interactions between OBP LUSH and ethanol, which might facilitate more rapid or successful OR binding of pheromone odorants within the sensillum lymph.…”

“…More research will continue to be needed to understand how ethanol changes pheromone detection dynamics, including across the more recently reclassified antennal intermediate sensillum types (i.e., ai2 and ai3), which were formerly known as trichoids (at2 and at3) (53,70,94). However, the OSNs within these trichoid and intermediate sensillum types (expressing Or67d, Or47b, and Or83c) did not strongly respond directly to ethanol when it was presented alone (53,56,94,95), nor did mutants with increased or decreased LUSH expression completely change their behaviors associated with ethanol (58,59,62,134). Additional OSNs and neural pathways for general alcohol detection and attraction thus remain elusive and do not appear to be exclusively linked to only trichoid-and pheromone-detecting OSN types on the fly antenna.…”

“…Products of fermentation are well-documented as the primary attractive substrates for adults across the model fly genus Drosophila. The relevant behaviors include attraction to sources of fermentation as sites for aggregation (6), feeding (46), fighting (94,95), courtship (10,139), and oviposition (12,25,47). In fact, despite differences in preference for specific sources and stages of fermentation (50,55), such as various fruits and even nonplant materials, most described Drosophila species overlap in their attraction to decaying host substrates, usually accompanied by large-scale microbial activity, especially yeast (6,31,61,75,100).…”