Summary Traumatic 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.

Frequency comparison is one of the most efficient ways to evaluate the performance of a frequency standard. Based on the pre-existing 40 Ca + optical frequency standard, we set up the second 40 Ca + optical frequency standard, which has been improved in the materials and structure of ion traps for better control of the magnetic field. After the compensation, the residual magnetic field at the position of the ion is adjusted to be ∼500 nT with a long time jitter of ∼10 nT, which is better than the pre-existing 40 Ca + optical frequency standard. We realize the '4-point-closed-loop locking' on the second 40 Ca + optical frequency standard after a series of preparatory works. Through half an hour of measurement time, the two frequency standards exhibited a stability of 2.1 × 10 −13 𝜏 −1/2 and a relative frequency difference of 1.5 (2.9) Hz.

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