GABAergic neurons in the dorsal raphe nucleus regulate social hierarchy in mice

Social hierarchy serves as a fundamental organizational mechanism within most animal societies, exerting significant influence on health, survival, and reproductive success in both humans and animals. However, the neural mechanisms by which the brain regulates dominance hierarchies remain inadequately understood. Considering that GABAergic neurons in the dorsal raphe nucleus (DRN) exert substantial inhibitory control over serotonergic firing, which may be implicated in the acquisition of dominance, we hypothesized that DRN GABAergic neurons may play a pivotal role in regulating social hierarchy. To test this hypothesis, we employed a combination of optogenetics, chemogenetics, fiber photometry recordings, and behavioral assays in mice, to elucidate the functional contributions of these neurons. Our results revealed a biphasic activity pattern of DRN GABAergic neurons, characterized by increased firing during retreats and decreased firing during push-initiation in the tube test. Furthermore, the optogenetic and chemogenetic activation of DRN GABAergic neurons led to an increase in the number of retreats and a reduction in social rank, while inhibition of these neurons produced the opposite effects. These findings elucidate the bidirectional regulatory role of DRN GABAergic neurons in social hierarchies.