Dorsal hippocampal oxytocin receptor regulates adult peer bonding in rats

Healthy social relationships are beneficial whereas their breakdown is often linked to psychiatric disorders. Parental care and bonding between sexual partners have been well studied both at the level of behavioral analysis and underlying neuronal mechanisms. By contrast, little is known about the neural and molecular basis of peer bonding, defined as social bonds formed between unrelated individuals of the same sex, due to the lack of a suitable experimental paradigm. We found that adult Sprague Dawley (SD) rats of the same sex form strong peer bonds with each other following co-housing. Peer bonded rats exhibit affiliative displays toward their cagemates who are distressed whereas they exhibit agonistic behaviors toward strangers in these situations. Using innovative, genetic strategies in rats, we show that both oxytocin receptor (OXTR) bearing neurons and Oxtr signaling in the dorsal hippocampus are essential for peer bonds to form. Together, we have developed a new platform for studying peer bonding and demonstrate a neural pathway that governs this behavior.