Serotonin Signals Overcome Loser Mentality in Drosophila.

Shao Wei Hu,Yin Peng Zhan,Yan Tong Yang,Yuanjie Sun,Yan Zhu

doi:10.1016/j.isci.2020.101651

Abstract

SummaryTraumatic experiences generate stressful neurological effects in the exposed persons and animals. Previous studies have demonstrated that in many species, including Drosophila, the defeated animal has a higher probability of losing subsequent fights. However, the neural basis of this “loser effect” is largely unknown. We herein report that elevated serotonin (5-HT) signaling helps a loser to overcome suppressive neurological states. Coerced activation of 5-HT neurons increases aggression in males and promotes losers to both vigorously re-engage in fights and even defeat the previous winners and regain mating motivation. P1 neurons act upstream and 5-HT1B neurons in the ellipsoid body act downstream of 5-HT neurons to arouse losers. Our results demonstrate an ancient neural mechanism of regulating depressive behavioral states after distressing events.

Highlights

Aggression is widespread in the animal kingdom as an important form of social behavior
Various populations of neurons in socially isolated flies were selectively treated by optogenetics with photoactivated adenylyl cyclase a (PACa), which rapidly increases cyclic adenosine monophosphate levels in the neurons after light stimulation (Schroder-Lang et al, 2007)
When two naive males were pitted in a fighting chamber for Round 1, most naıve-naıve pairs formed a clear winner-loser relationship within 30 min: the loser fled while the winner chased and attacked it (Figure 1A and Video S1)

Summary

Introduction

Aggression is widespread in the animal kingdom as an important form of social behavior. As stressful and sometimes lifethreatening experiences, aggressive encounters have long-lasting effects and change the mental states of the animals (Ehlers and Clark, 2000; Hofmann and Stevenson, 2000; Hsu and Wolf, 1999; Rutte et al, 2006). Mice exhibit a ‘‘winner effect’’ in which prior winning increases aggression and the probability of subsequent victory. A ‘‘loser effect’’ is common in many animals, in which a prior losing experience decreases the probability of an individual winning a subsequent fight (Hsu and Wolf, 1999; Rutte et al, 2006). An individual with losing experiences is less likely to initiate a confrontation and exhibits an increased tendency to retreat when challenged (Hsu and Wolf, 2001)

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Discussion

Conclusion