A hypothalamic pathway that suppresses aggression toward superior opponents.

Aggression is costly and requires tight regulation. Here we identify the projection from estrogen receptor alpha-expressing cells in the caudal part of the medial preoptic area (cMPOA Esr1 ) to the ventrolateral part of the ventromedial hypothalamus (VMHvl) as an essential pathway for modulating aggression in male mice. cMPOA Esr1 cells increase activity mainly during male-male interaction, which differs from the female-biased response pattern of rostral MPOA Esr1 (rMPOA Esr1 ) cells. Notably, cMPOA Esr1 cell responses to male opponents correlated with the opponents' fighting capability, which mice could estimate based on physical traits or learn through physical combats. Inactivating the cMPOA Esr1 -VMHvl pathway increased aggression, whereas activating the pathway suppressed natural intermale aggression. Thus, cMPOA Esr1 is a key population for encoding opponents' fighting capability-information that could be used to prevent animals from engaging in disadvantageous conflicts with superior opponents by suppressing the activity of VMHvl cells essential for attack behaviors.