Posterior Amygdala Regulates Sexual and Aggressive Behaviors in Male Mice

Sexual and aggressive behaviors are fundamental to animals’ survival and reproduction. The medial preoptic nucleus (MPN) and ventrolateral part of ventromedial hypothalamus (VMHvl) are essential regions for male sexual and aggressive behaviors, respectively. While key inhibitory inputs to VMHvl and MPN are identified, the extra-hypothalamic excitatory inputs essential for the social behaviors remain elusive. Here we identify estrogen receptor alpha (Esr1) expressing cells in posterior amygdala (PA) as a main source of excitatory inputs to hypothalamus and key mediators for mating and fighting in male mice. We find two largely distinct PA subpopulations that differ in connectivity, gene expression, in vivo responses and social behavior relevance. MPN projecting PA(Esr1+) cells are activated during mating and necessary and sufficient for male sexual behaviors, while VMHvl projecting PA(Esr1+) are excited during inter-male aggression and promote attacks. These findings place PA as a key node in both male aggression and reproduction circuits.