Effects of nucleus accumbens oxytocin and its antagonist on social approach behavior.

Severe impairment of social interaction is a core symptom of numerous psychiatric disorders. Oxytocin (OT) has been shown to be involved in various aspects of social behavior related to reproduction, but little is known about its effects on nonreproductive social interaction between adults or the neuroanatomical location where OT exerts its action. Here, we examined the nucleus accumbens, a region of the brain containing high levels of the oxytocin receptor (OTR) and comprising an important node in the neural circuitry possibly related to social interaction. Behavioral effects of a local microinfusion of OT (0.1, 1, and 10 ng/side) and an oxytocin receptor antagonist (OTR-A) (1, 10, and 100 ng/side) were evaluated in naturally high social and low social female and male monogamous mandarin voles (Microtus mandarinus) using the social preference paradigm and open-field tests. The results showed that administration of 1 ng/side OT increased social preference; however, this effect was not apparent at lower or higher doses. OT did not alter anxiety-like behavior or total locomotion. Microinfusions of a selective OTR-A at 10 and 100 ng doses reduced social approach behavior; a dose of 1 ng had no effect. In conclusion, our results suggest that accumbal OT and OTR-A regulate social preferences in voles in a dose-dependent manner.