GABA transmission from mAL interneurons regulates aggression in males.

Aggression is known to be regulated by pheromonal information in many species. But how central brain neurons processing this information modulate aggression is poorly understood. Using the fruit fly model of , we systematically characterize the role of a group of sexually dimorphic GABAergic central brain neurons, popularly known as mAL, in aggression regulation. The mAL neurons are known to be activated by male and female pheromones. In this report, we show that mAL activation robustly increases aggression, whereas its inactivation decreases aggression and increases intermale courtship, a behavior considered reciprocal to aggression. GABA neurotransmission from mAL is crucial for this behavior regulation. Exploiting the genetic toolkit of the fruit fly model, we also find a small group of approximately three to five GABA central brain neurons with anatomical similarities to mAL. Activation of the mAL resembling group of neurons is necessary for increasing intermale aggression. Overall, our findings demonstrate how changes in activity of GABA central brain neurons processing pheromonal information, such as mAL in , directly modulate the social behavior of aggression in male-male pairings.