Lateral hypothalamus to dorsal raphe nucleus projections modulate intraspecific attack behavior in male mice.

Aggressive behavior comprises distinct components, including threat displays and direct physical attacks, that typically occur in a coordinated sequence. Here, we identify the lateral hypothalamus (LH) to dorsal raphe nucleus (DRN) projection as a key pathway that bidirectionally and selectively controls attack bites while leaving threat displays intact in male mice. Optogenetic activation of this pathway enhanced attack bites without affecting threats during intermale aggression and sustained attacks toward female intruders when such behavior would normally cease. This pathway activation also induced place avoidance, suggesting it generates aversive states that may drive aggressive arousal. Both chemogenetic and optogenetic inhibition selectively reduced attack bites without altering threat displays. These findings establish the LH-DRN projection as a functionally defined circuit that dissociates the regulation of direct physical aggression from social signaling, providing insights into how distinct aggressive components can be independently controlled and potentially contributing to maladaptive aggression patterns.