Activation of basolateral amygdala in juvenile C57BL/6J mice during social approach behavior

• Juvenile C57BL/6J male mice exhibit high social approach behavior in a three-chamber apparatus.
• Social approach preferentially activates the basolateral amygdala (BLA), indicated by increased c-Fos and Egr-1 expression.
• Our data indicate that the BLA is an important hub in the circuitry mediating juvenile social approach behavior.
• Future studies of sociability in mouse models of ASD should address potential alterations in circuitry involving the BLA.

There is a strong need to better understand the neurobiology of juvenile sociability (tendency to seek social interaction), a phenotype of central relevance to autism spectrum disorders (ASD). Although numerous genetic mouse models of ASD showing reduced sociability have been reported, and certain brain regions, such as the amygdala, have been implicated in sociability, there has been little emphasis on delineating brain structures and circuits activated during social interactions in the critical juvenile period of the mouse strain that serves as the most common genetic background for these models—the highly sociable C57BL/6J (B6) strain. We measured expression of the immediate early genes Fos and Egr-1 to map activation of brain regions following the Social Approach Test (SAT) in juvenile male B6 mice. We hypothesized that juvenile B6 mice would show activation of the amygdala during social interactions. The basolateral amygdala (BLA) was activated by social exposure in highly sociable, 4-week-old B6 mice. In light of these data, and the many lines of evidence indicating alteration of amygdala circuits in human ASD, future studies are warranted to assess structural and functional alterations in the BLA, particularly at BLA synapses, in various mouse models of ASD.