Sleeping off stress:Social defeat activates midbrain cells, promoting sleep and reducing anxiety in mice.

When a mouse is placed in the cage of an aggressive conspecific (the “resident”), usually the intruder is quickly defeated. This experience of social defeat causes stress to the intruder. When social defeat takes place during the inactive phase of the day, most of the defeated animals subsequently fall asleep. On page 63 of this issue, Yu et al. (1) show that a small group of cells in the ventral tegmental area (VTA), projecting to the lateral hypothalamus, is activated by social defeat. This pathway is key to restorative sleep after social defeat, preventing a lasting state of anxiety.