RESUMO
Oxytocin plays important roles in the social and emotional behaviors of mammals. In the present study, we examined the effects of intraperitoneal (IP) and intracerebroventricular (ICV) injections of oxytocin on these behaviors in pubertal male mice. Male C57BL/6J mice received IP injection of oxytocin (high-dose group: 1 mg/kg, low-dose group: 0.1 mg/kg), and ICV injection of oxytocin (0.5 µg/2 µL). Behavioral tests were conducted after administration of oxytocin at the age of 5-7 weeks. IP injection of high-dose oxytocin attenuated social investigation behavior toward both a novel and a cagemate mouse in the social preference test, and enhanced anxiogenic behavior and reduced general activity in the light-dark transition and elevated zero-maze tests. In contrast, ICV injection of oxytocin enhanced social investigation behavior toward both stimulus mice in the social preference test, and had no effects on anxiety-related behavior but increased general activity in the light-dark transition, elevated zero-maze, and open field tests. These results suggest that IP and ICV injections of oxytocin have significantly different effects on social and emotional behaviors in pubertal male mice. IP injection of oxytocin (1 mg/kg) appears to reduce social investigation behaviors and enhance anxiety-related behaviors, while ICV injection of oxytocin appears to enhance social investigation behaviors and general activity.
