Abstract
Social recognition is fundamental for social decision making and the establishment of long-lasting affiliative behaviors in behaviorally complex social groups. It is a critical step in establishing a selective preference for a social partner or group member. C57BL/6J lab mice do not form monogamous relationships, and typically do not show prolonged social preferences for familiar mice. The CA2 hippocampal subfield plays a crucial role in social memory and optogenetic stimulation of inputs to the dorsal CA2 field during a short memory acquisition period can enhance and extend social memories in mice. Here, we show that partner preference in mice can be induced by chemogenetic selective stimulation of the monosynaptic projections from the hypothalamic paraventricular nucleus (PVN) to the CA2 during the cohabitation period. Specifically, male mice spend more time in social contact, grooming and huddling with the partner compared to a novel female. Preference was not induced by prolonging the cohabitation period and allowing more time for social interactions and males to sire pups with the familiar female. These results suggest that PVN-to-CA2 projections are part of an evolutionarily conserved neural circuitry underlying the formation of social preference and may promote behavioral changes with appropriate stimulation.
Highlights
The evolution of social behaviors and mating strategies is naturally affected by the environment in which a species has to survive
Avpr1b knock-out mice showing decreased social motivation (Wersinger et al, 2004) and accumulated evidence supporting vasopressin involvement in affiliative behavior across species (Caldwell et al, 2008; Williams Avram and Cymerblit-Sabba, 2017), we aimed to investigate the effect of stimulating the PVNto-dorsal hippocampal CA2 area (dCA2) projection on opposite-sex partner preference
Histology hM3D(Gq) receptor or m-Cherry were delivered by herpes simplex virus (HSV) bilaterally into the dCA2 to allow retrograde transport to projecting neurons, including the paraventricular nucleus (PVN), and onset of neuronal expression
Summary
The evolution of social behaviors and mating strategies is naturally affected by the environment in which a species has to survive. Pair bonding is a long-lasting preferential association between two sexually mature adults, often described in the monogamous prairie vole, that includes the formation of partner preference, selective aggression toward unfamiliar conspecifics and bi-parental care of the offspring. Selective affiliation toward a familiar conspecific is an inherent aspect of opposite-sex pair bonding and a critical step in the formation of enduring relationships (Young et al, 2011). While mating styles may differ, prosocial behaviors such as selective affiliation toward a familiar peer are observed across monogamous and even promiscuous voles (Lee et al, 2019). This social selectivity has been suggested to underly the establishment of vole social structure.
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