Capturing Dynamic Neuronal Responses to Dominant and Subordinate Social Hierarchy Members with catFISH

Dominance hierarchies are key to social organization in group-living species, requiring individuals to recognize their own and others' ranks. This is particularly complex for intermediate-ranking animals, who navigate interactions with higher- and lower-ranking individuals. Using in situ hybridization, we examined how the brains of intermediate-ranked mice in hierarchies respond to dominant and subordinate stimuli by labeling activity-induced immediate early genes and neuronal markers. We show that distinct neuronal populations in the amygdala and hippocampus respond differentially across social contexts. In the basolateral amygdala, glutamatergic Slc17a7+ neurons, particularly dopamine-receptive Slc17a7+Drd1+ neurons, show elevated IEG expression in response to social stimuli, with a higher response to dominant over subordinate animals. Similar patterns are observed among Slc17a7+Oxtr+ neurons in the dorsal endopiriform nucleus and GABAergic Slc32a+ neurons in the medial amygdala. We also identified distinct neural ensembles selectively active in response to dominant and subordinate hierarchy members. We find a higher degree of reactivation among Slc17a7+Oxtr+ ensembles in the dorsal endopiriform nucleus in animals repeatedly presented with the same hierarchy member, as opposed to those presented with a dominant and subordinate member. We observe a similar pattern among Oxtr+ neurons in the dentate gyrus hilus, while the inverse is observed among Slc17a7+ Avrp1b+Oxtr+ neurons in the distal CA2CA3 region. Collectively, our findings reveal how social context is associated with activity changes in social, olfactory, and memory systems in the brain at the neuronal cell type level. This work lays the foundation for further precise cell-type investigation into how the brain processes social information.