Chemogenetic activation of the amygdala core nucleus increases aggression in chickens.

Aggressive behavior is widely conserved across animal species and is often reduced during domestication. Recent advances in neurotechnology using adeno-associated virus (AAV) have enable identification of neural circuits underlying aggression in rodents, whereas those in domesticated birds remain poorly understood. Here, we applied a chemogenetic strategy using AAV-mediated expression of designer receptors exclusively activated by designer drugs (DREADDs) in chickens. Immunostaining of c-Fos following fight showed neuronal activation in the amygdala core nucleus (ACo), the amygdala intermedioanterior nucleus, and the ventromedial hypothalamic nucleus. AAV successfully transduced DREADDs in the chicken ACo. The frequency of aggressive behavior was higher under deschloroclozapine treatment condition than under dimethyl sulfoxide control at the first and second administrations, whereas this effect returned to baseline levels by the final administration. These findings suggest brain region-specific chemogenetic modulation of aggression in chickens and provide new insight into the neural basis of social behavior in domesticated animals.