摘要：SummaryTraumatic experiences generate stressful neurological effects in the exposed persons and animals. Previous studies have demonstrated that in many species, includingDrosophila, 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.Graphical AbstractDisplay OmittedHighlights•Activating a small subset of serotonin neurons promotes losers to fight•Serotonin is necessary and sufficient for modulating aggression in losers•The neural circuit for motivating losers includes P1, 5-HT, and 5-HT1B neurons•Elevating 5-HT signaling overcomes the depressive behavioral state in losersBehavioral Neuroscience; Molecular Neuroscience; Cellular Neuroscience
