Social encounters are associated with varying degrees of emotional arousal and stress. The mechanisms underlying adequate socioemotional balance are unknown. The medial amygdala (MeA) is a brain region associated with social behavior in mice. Corticotropin-releasing factor receptor type-2 (CRF-R2) and its specific ligand urocortin-3 (Ucn3), known components of the behavioral stress response system, are highly expressed in the MeA. Here we show that mice deficient in CRF-R2 or Ucn3 exhibit abnormally low preference for novel conspecifics. MeA-specific knockdown of Crfr2 (Crhr2) in adulthood recapitulated this phenotype. In contrast, pharmacological activation of MeA CRF-R2 or optogenetic activation of MeA Ucn3 neurons increased preference for novel mice. Furthermore, chemogenetic inhibition of MeA Ucn3 neurons elicited pro-social behavior in freely behaving groups of mice without affecting their hierarchal structure. These findings collectively suggest that the MeA Ucn3–CRF-R2 system modulates the ability of mice to cope with social challenges.
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NCBI Reference Sequence
We thank S. Ovadia for his devoted assistance with animal care. We thank J. Keverne for professional English editing, formatting and scientific input. This work is supported by an FP7 grant from the European Research Council (260463; A.C.); research grants from the Israel Science Foundation (1565/15) (A.C.); research support from Roberto and Renata Ruhman (A.C.); research support from Bruno and Simone Licht; I-CORE Program of the Planning and Budgeting Committee and The Israel Science Foundation (grant no. 1916/12 to A.C.); the Nella and Leon Benoziyo Center for Neurological Diseases (A.C.); the Henry Chanoch Krenter Institute for Biomedical Imaging and Genomics (A.C.); the Perlman Family Foundation, founded by Louis L. and Anita M. Perlman (A.C.); the Adelis Foundation (A.C.); the Irving I. Moskowitz Foundation (A.C.); grants from the Israel Science Foundation (1351/12) and the European Commission (ERC StG #337637 and Marie Curie CIG #321919) (O.Y.) and a Human Frontier Program career development award (O.Y.); a Human Frontier Science Program grant (E.S.); European Research Council grant # 311238 (E.S.); an Israel Science Foundation grant #1629/12 (E.S.); research support from Martin Kushner Schnur (E.S.); and Mr. and Mrs. Lawrence Feis (E.S.).
Integrated supplementary information
MeA Ucn3-expressing neurons were optogenetically activated while the mouse was tested in the social maze. The maze comprised three arms: one with a mouse familiar to the actor, another with a novel mouse, and the third empty (non-social). The arm that contained the familiar mouse can be recognized in the movie by the note "F" below it.
The video shows the tracked position of each of four mice. As mice are nocturnal, we recorded them in low light conditions that mimic a bright night (2 lux). Each mouse was marked using a different hair dye, which due to the use of sensitive cameras was distinguishable even under these light levels. The arena contained nests, feeders, water, and additional enrichments which are highlighted in the video.
Each contact between the mice was analyzed to determine which behavior preceded it (who initiated the interaction), and how it concluded. Interactions that ended with one mouse going after the other while the other moves away were automatically classified as an aggressive chase-escape or as non-aggressive.